question from my buyer

So I have a buyer that I found trough my marketing that wants to buy an owner financed home. He asked me a question about payments that I was not able to answer. He will put down 10k and he wants something under $100k. How can estimate what his payments will be under owner financing . Im still unclear on this. Any advice is appreciated.

Depends on taxes and the interest rate.
I know that’s vague, but those are the 2 biggest items.
Here in Texas taxes seem to be higher than others areas, so it’s not uncommon for taxes to be $400 or $600 a month!