Those are big questions.
The Seller's Role is to pretend to be the Bank.
It can be safe IF the Seller performs his Due Diligence. Few do.
Most Mortgages prohibit turning over control of the Collateral to another party without the Mortgagee's Approval, so as a practical matter, Owner Financing is usually restricted to the consideration of only those Sellers who own their property outright.
Here's some prior discussion:
Owner Financing/Rent to Own/Lease Purchase As the Title implies, I lump them all together.
Use the
Search Box to the right to investigate each of them separately. --->
Put quotes around "multi-word searches".
Good Luck.