Even at the lowest income bracket, there are buyers who can put together 10% down on a $12,000 house - even some who can put together 20%. If you owner finance such a sale, and charge interest rates that make the monthly mortgage competitive with rent elsewhere, you can do very well for yourself.
https://www.ortconline.com/Web2/Downloads/English/CFPB%20and...
Unfortunately some people are forced into that arrangement simply because otherwise they'll never be able to offload it. It is something to keep in mind when getting into these types of property.
PS - Keep in mind that if you receive cash for this property you could use it as a downpayment on another, without getting all of the cash up-front you'll have to take out a bigger mortgage against your next property which will cost you money in interest over the life of the loan. So even ignoring the administrative hassle of seller financing, you're now also out of pocket.