So this is the problem with rent credit -- the contract goes between the person in the home and the person who owns the homes plural. If it's just a single home and the credit "applies" only to a pool of one home, it looks a lot like an illegal mortgage.
If the pool includes a home the person is living in and that is sold out from under them, what happens to the credits? The rent credit contract should address this, but there is a lot that smells like fraud or deceptive trade practices if the park-owned homes transfer and the credits don't. Who sets the price of the homes for sale at a certain price (in credits?). Is it arbitrary? You can argue with buyer about how much the homes are really worth ($5500 to buyer in your hypo at $10k to you, because there come pre loaded with $4500 "credit" towards a fixed price of $10k) and come out somewhere.
But over time surely the homes are worth less and less so the RC contract should not specify a price. Does it? If so, looks more like an lease option than a RC.
If the price is arbitrary, the homes are worth what they are worth, and the liability is what it is, and you and the buyer have to decide what your contract says is supposed to happen and whether you like that or not (is it a deal killer).