Even if you can afford it, is it the best thing for you to do?

Their mortgage is too high for them to afford but with my income/credit, I'd be able to purchase their property.

This is trickier because you don't want to wait until they can't afford the property.

If you’d be heart broken if you lost the property, make sure you don’t take out a bigger loan than you can afford to pay with zero rent coming in.

Discusshttps://wtop.com/dc/2020/01/dc-lawmaker-hopes-bill-will-protect-affordable-housing-and-increase-tenant-protections/

Section 8 adds a standardized lease, annual inspection and a subsidy to enable the prospect to afford your rental.You and Tenant sign your lease and the S8 lease. 

Or more, beacuse it’s more affordable then buying a home.  

Even with "rent stabilization", rents are still increasing faster than wages in these markets; ergo, the voters will eventually require their lap dogs....err, I mean representatives to pass new laws to make housing "affordable". 

Good schools also make your property sticky, in that people don't want to leave if the rental gives them a chance to send their kids to school in an area where they cannot afford to buy a home.Some other things to consider - what I call "anchors."  

@Kevin Moore house hacking the first deal is by far the best way to start because you get your personal finances in order (save dat money), you get to learn to be a landlord with training wheels, you get to use a lower down-payment and preserve cash, you have more intimate knowledge of what's going on at your building, you can buy in a higher value area because you can afford more, and tons of other benefits discussed ad nauseam on Bigger Pockets.