Focus on the actual deal first.

Or maybe the units aren't equal and one rents for $2800 covering most of the cost of living there. 

I can only come out of pocket to cover mortgage so long.  

And all of that with training wheels, it is very hard to screw it up on a consequential scale.Because it is 2025 and RE is not cheap anymore I will encourage you to also look into building a business on the side.

Sellers may struggle to mentally shift from "owner" to "tenant," which can create challenges with boundaries and property care.Security Deposit:If you’re doing a temporary leaseback, be sure to collect a substantial security deposit to cover potential damages and ensure they vacate on time.

The best deal in the world can get screwed up by poor management.

As long as the rents can cover both the current PITI and proposed P&I payment, credit is at least 680. you should be able to qualify. 

You only get a single point of contact for everything all encompassing, and unless they are 100% competent(not even proficient) you are screwed.

Quote from @Dustin Calgaro: Man I really screwed that math up, I didn’t compound the appreciation.

I have a one page lease addendum to cover this, that is executed with every tenant and every lease.