And that's a US and TX constitutional question because this is a taking. 

I am all for paying an agent that is involved in the sale, but merely sticking a sign in the yard does not constitute earning a commission.

It will be implied that this letter shall constitute a legally binding contract, enforceable under federal and state law.

I sent her an invoice however if I take her to court will I have to furnish the actual receipts or will the invoice constitute proof?  

Is there a provision that repeated late payment constitutes grounds for an eviction?

Most traditional bank loans already have the Feds involved, so they figure that they can also regulate the actual transaction if the parties are using their already-regulated loans.Disclosure: I am not an attorney, CPA, or Constitutional Scholar, just a regular guy who can read.

I would talk to an 1031 exchange expert to get clear on what would constitute an investment property so that you don't have to sell (maybe a short term rental for one of the rooms or something).

If the buyer accepts the property (as is) with prior written knowledge by (seller disclosure) then that could constitute an (AS IS) scenario.

Do you know what constitutes a valid deed?

Hi, that has nothing to do with funds being received by another lender, which won't be on that transaction, what they are talking about is credits back to a buyer that constitutes less in the deal than as contracted, you are not to be walking away with cash after settlement.