I dissent.

(1) Although appellant expressly conceded in her opening brief that the agreement signed by her on February 14, 1945, did not create a mortgage and “could not ... be construed as security for the note,” respondent’s brief contains a needless argument that the agreement was security for the note and that she waived the security in order to sue on the note. Since a defense on that ground was not made by appellant at the trial and is renounced on the appeal the discussion of the subject in Mr. Justice McComb’s opinion is unnecessary and answers a nonexistent question.

(2) The promissory note sued on and the agreement were executed contemporaneously, were parts of the same transaction, and must be read and construed together as if they were one instrument. Appellant, while testifying under section 2055 of the Code of Civil Procedure, identified her signature on the promissory note and stated “but along with that was a contract which was attached to it at the time.” Respondent’s counsel then produced the agreement which was identified by appellant and received in evidence. Appellant was asked by respondent’s counsel whether she had given respondent any money or agreed to pay her any money other than that represented by the promissory note. Appellant responded: “No, I didn’t agree to give her any money. I didn’t owe her any money until the lot was sold, which we entered into a business arrangement, an agreement. We were partners in a business agreement. And I owed her no money until she sold the lot. ’ ’ In answer to a question by the court appellant *485 testified: “Mrs. Lederer knew that we were unable to buy the full three acres at 2020 Cold Water Canyon, and she told us she had a buyer for one acre, or one parcel of property, which would enable us to buy the remaining two acres and house, which we wanted. Well, the buyer never materialized, so we entered into a business arrangement whereby she would leave the commission, not take her commission out until such time as she had sold that lot that she had agreed to sell, and it was simply to remain in status quo until the lot was sold; and at such time as—and we had a written agreement to that effect—at such time as the lot was sold she was to have her $2,400, which she would still be going to have if she had sold the lot. But the lot has not been sold. Nor-—-I believe there has been no effort to sell the lot. ’ ’

Appellant’s evidence was corroborated by that of her husband who testified concerning the conversations leading up to the signing of the promissory note and the agreement as follows: “Mrs. Lederer discussed the sale of her house and the possible buying of another one. I told Mrs. Lederer that I was perfectly willing to change houses if Mrs. Muir would be happier, providing I didn’t have to invest one nickel, that I didn’t have it. I also told her that I was a free lance actor and I didn’t know when I would work again, whether tomorrow or a year from tomorrow. . . . Under the circumstances, with no income, no employment, it is utterly ridiculous that you would have any deal or proposition by which I could pay the Lederers $2400 until I could sell this extra land. This was a $30,000 house which I could never afford until I acquired that $11,000 to help me out. I made that agreement very clear. And under no circumstances would we have entered into such a deal, regardless of anything that might appear in the writing in the contract. It is my fault, I suppose, by not getting an attorney and by having so much faith in Mrs. Lederer’s integrity and intentions.”

Respondent was not called as a witness in her own behalf. Her husband testified that he prepared the promissory note, filling in the blanks in a printed form, and that the agreement was dictated in his presence.

No evidence whatsoever was offered contradicting that of appellant and her husband. Patently the two instruments are a part of one transaction and must be so read. The note and the agreement are both dated February 14, 1945. "The *486 note provides: “As per written agreement of even date on demand after date, for value received, the undersigned” promises to pay, etc. The last sentence of the note, which follows the printed portion, was written by respondent’s husband in her behalf and reads: “This note is given as security and agreement to repay the sum of $2400. cash loaned to Frances Muir by Mary Helena Lederer.” The agreement, after reciting that respondent loaned the sum of $2,400 to appellant, provides: “To secure the above $2,400.00, the undersigned, Frances Muir, agrees to return said $2,400.00 from the sale of the vacant south portion of 2020 Cold Water Canyon property, . . . This loan and agreement is secured by Note of even date herewith.” The quoted language of the agreement was not, as stated in each of the opinions of the majority, “additional security for the note.” In fact there was no security for the payment of the note. The agreement placed a limitation on the payment, to wit, that payment was not to be made or required save from the sale of the property described. Emphasizing this view is the language of the note itself that it is to be paid “as per written agreement of even date,” that is, from the sale of the property.

Each instrument refers to the other in such manner as to require them to be read as one document. The note is to be paid "as per written agreement of even date ’ ’ and the agreement purports to be secured “by note of even date herewith.” It is obvious, however, that the agreement was not secured by the note. Moreover, the oral evidence leading up to their execution, which was introduced not for the purpose of changing the terms of either instrument but of showing their interrelation, conclusively demonstrates that neither document would have been executed without the other. The note would not have been executed except for the agreement providing for its payment from the sale of the Coldwater Canyon property and the agreement would not 'have been signed except for the purpose of specifying the manner of payment of the note. The two documents and the uncontradicted evidence show that the intention of the parties was (1) that the note was not payable until after the property referred to in the agreement had been sold, and (2) that the note was not a demand note in the ordinary legal significance of that term but that it was payable on demand only “as per written agreement of even date,” that is after the Coldwater Canyon property had been sold. The only reasonable and rational *487 conclusion that can be placed upon the two documents is that demand for payment was not to be made except “as per written agreement of even date” which provided that appellant “agrees to return said $2,400.00 from the sale of” a portion of the Coldwater Canyon property.

Section 1642 of the Civil Code reads as follows: ‘ ‘ Several contracts relating to the same matters, between the same parties, and made as parts of substantially one transaction, are to be taken together. ’ ’ Where there is a contemporaneous written contract affecting the terms of a promissory note the contract must be construed with the note and any lawful condition added to the note by such collateral agreement may be enforced. (Goodwin v. Nickerson, 51 Cal. 166 , 169 ; Spotton v. Dyer, 42 Cal.App. 585, 588 [ 184 P. 23 ] ; Mutual Bldg. & Loan Assn. v. Beers, 117 Cal.App. 200, 204 [ 3 P.2d 565 ].) Where an obligation is payable upon the happening of a contingency it does not mature until the contingency occurs and the payee of the obligation is not entitled to recover in the absence of proof of such happening. (Clarey v. Security Portland Cement Co., 99 Cal.App. 783, 787 [ 279 P. 483 ] ; Lynch v. Keystone Consol. Mining Co., 163 Cal. 690, 698 [ 126 P. 968 ] ; Cantwell v. Gage, 111 Cal.App. 209, 212 [ 295 P. 375 ] ; Vatcher v. Grier, 50 Cal.App. 39, 41 [ 195 P. 75 ] ; Lind v. Huene, 205 Cal. 569, 576 [ 271 P. 1087 ].)

In Rosenfeld v. Miller, 1 Cal.2d 206, 211 [ 33 P.2d 1013 ], it was held that a real estate broker was-not entitled to recover his commission for the negotiation of a lease because certain conditions upon which the commission was to be payable had not been fulfilled. In Lindley v. Fay, 119 Cal. 239, 243 [ 51 P. 333 ], the agreement provided for the payment of commissions out of the first moneys received. No money having been received the court held that the broker was not entitled to his compensation although he had produced a purchaser ready, able and willing to purchase on the prescribed terms.

Where a contract limits the liability for payment to funds to be derived by the payor from a specified source, there can be no recovery in the absence of pleading and proof that the debtor had received funds from that source. (Martin v. Martin, 5 Cal.App.2d 591, 593 [ 43 P.2d 314 ] ; Lynch v. Keystone Consol. Mining Co., supra, at p. 698 ; Flippen v. Abbey, 135 Cal.App. 666, 671 [ 27 P.2d 792 ].)

*488 The proof is that the Coldwater Canyon property had not been sold at the time of the trial, hence there was no fund from which the loan made by respondent was payable, the note had not matured, and respondent’s cause of action had not accrued.

(3) The complaint alleged that at the time of the transaction referred to respondent was a licensed real estate broker. This allegation, as were all other allegations in the complaint, was denied by a verified answer. No evidence was introduced upon said allegation and the court’s failure to make a finding thereon was error. (Bus. & Prof. Code, § 10136.) Although the action is brought upon a promissory note executed by appellant the accompanying agreement recites that the sum of $2,400 loaned by respondent to appellant consisted of $900 commission due respondent upon the sale of appellant’s property on San Ysidro Drive and $1,500 derived from another source. The agreement recites that the sum of $900 is a commission due respondent as agent from the sale of the San Ysidro Drive property. If respondent was not a licensed real estate broker at the time of the sale she was not entitled to a commission from appellant and therefore had not earned the sum of $900 which she purported to loan to appellant. In that event the money agreed to be loaned to appellant was the latter’s own property.

For all the reasons stated the judgment and the order denying a new trial should be reversed.

A petition for a rehearing was denied May 19, 1947. Wilson, J., voted for a rehearing.

Appellant’s petition for a hearing by the Supreme Court was denied June 30, 1947. Traynor, J., and Carter, J., voted for a hearing.