A recent article from American Financial Network included this quote: “According to a new Survey from Freddie Mac, 34% of renters spend more than 1/3 of their income on rent, while only 25% of homeowners spend that much on their mortgage.”
Remember this data when you are negotiating with a borrower in a seller financed situation. If you can get the safest terms possible for yourself and keep the monthly payment at or below his current rent payment, you have a win-win for both parties.