The Rent Ordinance para (e) explicitly precludes that possibility:
Any waiver by a tenant of rights under this Chapter 37 shall be void
as contrary to public policy.
If he attempts to enforce such a clause or in any way dislodge you from the unit, he is liable for a substantial penalty.
The legality of a rebate scheme is not clear, but probably would also be deemed illegal, because there already exists provision for buyout, which has specific restrictions. For the rest of the week, tenant buyouts are subject to these provisions. The problem is that the horse may have left the barn. The landlord has to have provided you with a Pre-Buyout Disclosure Form (which is to be signed and filed) before any negotiation / discussion with the tenant. Since we're talking about obeying the law, it has to occur to the landlord that there is a buyout option, and then he has to give you and file the disclosure form before he opens his mouth. He also has to know what the requirements of a buyout agreement will be in the future. Starting on Monday, the law regarding buyouts changes (it doesn't clearly make an agreement impossible, but it's a reminder that the law can be changed). In terms of legally-enforceable agreements, you could agree to a buyout in the far future, but the agreement might not be enforceable under future law. For example, the disclosure form requires new information to be provided, so if he doesn't do that, the disclosure is invalid (the preamble to the amendment points out that the change in law was directed at legal actions that were considered to violate the spirit of the law). Hence a buyout for two years in the future is legally risky.