The house is a 3b/2ba 1,895 sq ft home but an additional sunroom built in which brings sq ft up to 2,055 (based off tax records my agent found).

Im not familiar with the specifics of the USA + Mexican tax treaty, but this article is a great place to start: https://www.cpasforexpats.com/post/us-mexico-tax-treaty#:~:text=The%20US%20Mexico%20tax%20treaty%2C%20signed%20in%201992%2C%20serves%20as,according%20to%20their%20respective%20laws.

Every day I wake up to look at Google News and there is at least one article about Foreclosure, or Fixed Income Tenant can't stay where they have been from before the Covid or the Widow who has lived in the 2/1 house for 50 years cannot pay the increases in Property Tax, Home Owner's Insurance, Lights, Water and everything else.

Worst case the irs says he should have charged interest and he owes $20-30 in taxes. 

CPAs that really know the back and front of not only fix and flip but investing write offs/tax liability. 

Seller financing still implies a transaction and therefore a tax event.

Also taxes are to be considered.

@Michael Shea I'm not a tax accountant, but I've done the rent by room strategy for over 6 years as a house hacker, and I've recognized rent by room tenants rents in the Schedule E part of the tax return.

Think of it like the escrows you likely pay your mortgage servicer for Insurance and Taxes, or your estimated taxes to IRS.  

Tax BenefitsIf you are down one but up the other three, it can make sense.