I guess I don’t follow. You mean a Contract for Deed, where the warranty deed is held in escrow, payments are made to/from an escrow collection account? That’s the only way to do it and be fair to both parties.
Once again, I have to say, SEPARATE THE POH’s. Make a completely separate deal for them. (They aren’t real estate anyway, so they shouldn’t be in the Contract for Deed.) Put them in a separate LLC from the park. Have a separate installment sale contract for them with the seller. Don’t price them in reference to income, price them in reference to their value today where they sit. Most used homes are not worth more than $10K, but seller’s often try to price them based on income, at the same cap rate as the real estate. You can’t pay $30K for a 20-year-old remodeled single-wide.