LOAN AGREEMENT

Exhibit 10.58

LOAN AGREEMENT

This LOAN AGREEMENT dated as of October 26, 2007 (“Agreement”) is executed by and between PETRA FUND REIT CORP., a Maryland corporation (“Borrower”), and KBS PREFERRED HOLDING I, LLC, a Delaware limited liability company (“Lender”).

RECITALS:

A. The Borrower desires to obtain certain loans from the Lender for its general corporate purposes and not for any specific investment.

B. Lender desires to make the loans to Borrower with funds Lender’s indirect parent, KBS Real Estate Investment Trust, Inc. (“KBS”) received in exchange for newly issued shares in KBS.

NOW THEREFORE, in consideration of the mutual promises herein contained and for other valuable consideration, the parties hereby agree as follows:

AGREEMENT:

“Constituent Documents” shall mean, for any entity, its constituent or organizational documents, including: (a) in the case of any partnership, joint venture, trust or other form of business entity, the partnership, joint venture, trust or other applicable agreement of formation or any agreement, instrument, filing or notice with respect thereto filed in connection with its formation with the secretary of state or other department in its state of formation, in each case as amended from time to time; (b) in the case of any limited liability company, the certificate or articles of formation and operating agreement; (c) in the case of a corporation, the certificate or articles of incorporation and the bylaws; and (d) any side letters or other agreements relating to the foregoing. Such term shall also include any loan documents or documents reflecting borrowings by such entity.

“Default” shall mean any event which, with the giving of notice or lapse of time or both, would become an Event of Default.

“Interest Rate” shall mean 11.5% per annum.

“Loan” and “Loans” shall mean, respectively, each advance and the aggregate of all such advances made by the Lender to the Borrower under and pursuant to this Agreement, as set forth in Section 2 of this Agreement.

“Loan Documents” shall mean this Agreement, the Notes (including any renewals, extensions, supplements, amendments, restatements, reissuances and refundings thereof), and any agreements or documents, any amendments, supplements, extensions thereto or modifications or restatements thereof executed or delivered by or on behalf of the Borrower pursuant to the terms of this Agreement or any of the foregoing.

“Maturity Date” shall mean the earliest of (a) eighteen (18) months after the date hereof with respect to Tranche A of the Original Loan, and twenty-four (24) months after the date hereof with respect to Tranche B of the Original Loan, and twenty-four (24) months after the date of the Additional Loan, or (b) the date upon which the Obligations are, or Lender declares the Obligations to be, as the case may be, due and payable after the occurrence and during the continuance of an Event of Default.

“Maximum Loan Amount” shall mean the principal amount of the Original Loan and the Additional Loan, and in no event will such amount exceed seventy-five million dollars ($75,000,000.00) in the aggregate.

“Millennium Debt” means that certain $30 million dollar loan made to the Borrower by Millennium Partners, L.P. on July 10, 2007 evidenced by that certain Petra Fund REIT Corp. Floating Rate Convertible Senior Note due 2008, a true and complete copy of which has been delivered to the Lender.

“Obligations” shall mean all present and future indebtedness, obligations and liabilities of every nature owing or accruing to the Lender pursuant to the terms of this Agreement or any other Loan Document, and all renewals, amendments, supplements, restatements, and extensions thereof, including, without limitation, all interest accruing thereon, and reasonable attorneys’ fees incurred in the enforcement of collection thereof, regardless of whether such indebtedness, obligations and liabilities are direct, indirect, fixed, contingent, joint, several or joint and several.

“Petra Offshore” shall mean and refer to Petra Offshore Fund L.P., a Cayman Islands exempted limited partnership.

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The Additional Loan may be made available subject to the Lender’s sole discretion when such Additional Loan is requested by the Borrower (it being understood and agreed that Lender shall have no liability for its failure or refusal to make the Additional Loan).

Each Loan shall be evidenced by the Borrower’s promissory note payable to the registered holder thereof, and such notes shall be in the form of Exhibit B attached hereto (each, a “Note” and collectively, the “Notes”). Any of the Loans made against the Notes and the status of all amounts evidenced by the Notes shall be recorded by the Lender or its agent on its books and records or, at its option in any instance, endorsed on a schedule to the Notes and the unpaid principal balance and status and rates so recorded or endorsed by the Lender shall be prima facie evidence in any court or other proceeding brought to enforce the Notes of the principal amount remaining unpaid thereon, the status of the Loans evidenced thereby and the interest rates applicable thereto, absent manifest error; provided that the failure of the Lender to record any of the foregoing shall not limit or otherwise affect the obligation of the Borrower to repay the principal amount of the Note together with accrued interest thereon. The Borrower agrees that in any action or proceeding instituted to collect or enforce collection of the Notes, the amount shown as owing the Lender on its records shall be prima facie evidence of the unpaid balance of principal and interest on the Notes, absent manifest error.

None of the Loans is a “revolving” loan and any portion of principal repaid or prepaid may not be re-borrowed.

All amounts paid on the Loans shall be paid by Borrower irrespective of, and without any deduction for, any setoff, defense or counterclaim.

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Notwithstanding anything to the contrary contained herein (a) all agreements and communications between Borrower and Lender are hereby and shall automatically be limited so that, after taking into account all amounts deemed interest, the interest contracted for, charged or received by Lender shall never exceed the maximum lawful rate or amount, (b) in calculating whether any interest exceeds the lawful maximum, all such interest shall be amortized, prorated, allocated and spread over the full amount and term of all principal indebtedness of Borrower to Lender, and (c) if through any contingency or event, Lender receives or is deemed to receive interest in excess of the lawful maximum, any such excess shall be deemed to have been applied toward payment of the principal of any and all then outstanding indebtedness of Borrower to Lender, or if there is no such indebtedness, shall immediately be returned to Borrower.

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For purposes hereof, “Yield Maintenance Premium” shall mean a premium equal to the greater of (a) .5% of the principal amount of the Note being prepaid or (b) the product of (i) a fraction, the numerator of which is the positive excess, if any, of (A) the present value of all future payments of principal and interest on the Note being prepaid, including the principal amount due on the Maturity Date, to be made on such Note as of the prepayment date in question and through and including the Payment Date that is six (6) months prior to the Maturity Date, discounted at an

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interest rate per annum equal to the sum of (x) the Treasury Constant Maturity Yield Index published during the second full week preceding the date on which such premium is payable for instruments having a maturity coterminous with the remaining term of such Note, over (B) the principal amount of such Note immediately before such prepayment, and the denominator of which is the principal amount of such Note immediately prior to the prepayment, and (ii) the principal amount of the Note being prepaid; provided, however, that if there is no Treasury Constant Maturity Yield Index for instruments having a maturity coterminous with the remaining term of such Note, then the index referred to in (A) above shall be equal to the weighted average yield to maturity of the Treasury Constant Maturity Yield Indices with maturities next longer and shorter than such remaining average life to maturity, calculated by interpolating the yields of the relevant Treasury Constant Maturity Yield Indices (rounded, if necessary, to the nearest  ¹/100 of 1%).

The Yield Maintenance Premium provided above shall be due, to the extent permitted by applicable law, under any and all circumstances where all or any portion of any Note is paid prior to its Maturity Date, whether such prepayment is voluntary or involuntary, even if such prepayment results from Lender’s exercise of its rights upon Borrower’s default and acceleration of the Maturity Date of such Note, and shall be in addition to any other sums due hereunder or under any of the other Loan Documents. No tender of a prepayment of a Note (or any portion thereof) with respect to which the Yield Maintenance Premium is due shall be effective unless such prepayment is accompanied by the Yield Maintenance Premium.

For purposes hereof, “Treasury Constant Maturity Yield Index” shall mean the average yield for “This Week” as reported by the Federal Reserve Board in Federal Reserve Statistical Release H.15 (519). If there is no Treasury Constant Maturity Yield Index for instruments having a maturity coterminous with the remaining term of this Note, then the index shall be equal to the weighted average yield to maturity of the Treasury Constant Maturity Yield Indices with maturities next longer and shorter than such remaining average life to maturity, calculated by averaging (rounded upward to the nearest 1/8 of 1% per annum) the yields of the relevant Treasury Constant Maturity Yield Indices (rounded upward to the nearest 1/8 of 1% per annum). In the event that there is no Treasury Constant Maturity Yield Index available, Lender may select an alternate index as may be reasonable based on the available indices.

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In addition to the foregoing, and within five (5) business days following request therefore from Lender, Borrower agrees to deliver to Lender a copy of any other financial statements and/or information prepared by Borrower for distribution to its shareholders. The delivery of each financial statement, report and summary described in this Section 7 shall be deemed to be a representation and warranty that each such statement, report and summary fairly presents in all material respects the financial condition of Borrower as of the applicable date of delivery.

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Notwithstanding anything to the contrary herein, a failure by Borrower to comply with this Section 7 in a manner that gives rise to an Event of Default shall not alone result in any acceleration of the Maturity Date of any Obligation hereunder.

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(B) In consideration of, and as an inducement to, the Lender’s agreement to make advances of Loans to the Borrower hereunder, the Petra Offshore hereby represents and warrants to the Lender that: (a) Petra Offshore is a limited liability company duly organized, validly existing, and in good standing under the laws of its jurisdiction of formation; (b) the execution, delivery, and performance by the Petra Offshore of this Agreement, is within its powers, has been duly authorized by all necessary action, and does not contravene the governing documents of Petra Offshore or any law or any contractual restriction binding on or affecting Petra Offshore; (c) no authorization or approval or other action by, and no notice to or filing with, any governmental authority, regulatory body or contractual counter party is required for Petra Offshore’s due execution, delivery, and compliance with this Agreement; (d) to the extent (but only to the extent) Petra Offshore is a party to this Agreement, this Agreement is the legal, valid, and binding obligation of Petra Offshore enforceable against it in accordance with its terms except as such enforceability may be limited by bankruptcy, insolvency, reorganization, moratorium or similar state or federal debtor relief laws from time to time in effect which affect the enforcement of creditors’ rights in general and the availability of equitable remedies.

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(b) It is expressly understood that the Lender has no, and assumes no, liability or responsibility for the performance of any duties, covenants, or agreements of the Borrower, whether hereunder or under any of the other Loan Documents, the Constituent Documents, or any other duties, covenants, or agreements of Borrower, or other control over the management and affairs of the Borrower, and under no circumstances shall any action by Lender, in exercising its rights and/or remedies hereunder or otherwise, be deemed to create a partnership or other related party arrangement with the Borrower.

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(b) This Agreement and the other Loan Documents are solely for the benefit of Lender and Borrower and nothing contained in this Agreement or the other Loan Documents shall be deemed to confer upon anyone other than Lender and Borrower any right to insist upon or to enforce the performance or observance of any of the obligations contained herein or therein. All conditions to the obligations of Lender to make the Loan hereunder are imposed solely and exclusively for the benefit of Lender and no other person or entity shall have standing to require satisfaction of such conditions in accordance with their terms or be entitled to assume that Lender will refuse to make a Loan in the absence of strict compliance with any or all thereof and no other person or entity shall under any circumstances be deemed to be a beneficiary of such conditions, any or all of which may be freely waived in whole or in part by Lender if, in Lender’s sole discretion, Lender deems it advisable or desirable to do so.

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This Agreement is dated as of the date first written above.

The undersigned has executed this Agreement to evidence its acknowledgment of, and agreement to, the terms of Sections 24 and 32 hereof.

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