Reasonable terms for seller financing

[David Cornett]

Hello,

There is a SFR on the market (1200 sqft, 3b/2ba). Sale price is $78K but the seller wants to finance the deal, requiring 5% down and $850/month for 20 years. This translates into $204K over the life, in addition to the small down payment.

Assuming the title is clear, is this a reasonable amount? It strikes me as too high of a payment considering a conventional loan at 5% APR would be about half that (not even considering the higher down payment). However, advertised seller financing seems rare, and this is probably negotiable.

Thanks for any adice!