Thank you for your reply. The document and language is unusual, so ultimately, if there is a dispute a court will have to interpret it based on the Statute of Frauds and evidence from both sides as to the formation, etc., of this agreement. So, no real way to say whether it is even enforceable, but it certainly, at least based on what you shared, does not place any time limits on any payment of funds to the other party.
That said, the statute of referred to above, is a common law theory of law, which has been codified under California law at CA Civil Code section 1624, that requires that contracts and agreements, title, etc., in land must be reduced to writing. This is a writing, however, because the deed is in your name only, any document that diverges from that actual deed as to title, is not likely enforceable. In other words, the part of the agreement that says you own as tenants in common, will not likely be enforceable since that is not what the actual ownership official document says. But again, a court would have to make that decision after a lot of briefing by opposing attorneys.
All that said, she can always try to file a quiet title action and ask for a forced partition requiring you to sell or pay her part of the value of the property. I think it is doubtful that this would be successful, but it could cost considerable legal fees to sort out. Therefore, if you can reach an agreement now, in order to avoid all of this litigation over the agreement and the split of money, you might be better off in the long run.
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