Bought a property via Subto existing mortgage - Selling via warp around owner financed via Contract for Deed (or Land Contract).

What qualifications should I put the retail buyer though? DTI? Etc

Should I use a note servicing company? If so, any recommendations on note servicing companies?

With this as a subto take over, does the end buyer need to get property insurance? Or should I just pay the underlying insurance? If so, what happens when there is a claim as the underlying insurance is under the old owner?