I was thinking I could put down the 50k so he had enough to pay off the heloc and make payments to him for the remainder to be paid off in 10 years with new renters.

Credit score shouldn't be the primary driver of tenant approval, because if they could qualify for a mortgage they probably wouldn't be renters.

The tenants should have renter's insurance to protect you.

By this point, they will have already thought about what might happen if you leave, including the need to turn over the unit and find a new renter.

Plus your renters will appreciate it because of your accessibility instead of being some faceless, detached, uncaring landlord. 

Talk to residents, potential buyers and renters to see what their thoughts are regarding home values in the areas. 

Does that mean I don't care about my renter?

Replacing a bathtub with a shower can make narrow bathrooms feel larger and more modern.That said, consider keeping at least one bathtub in the building for market appeal, as families with small children or certain renters may prefer it.

In the areas I’m in appropriately priced units rent very quickly to qualified renters.

Interestingly, though, people who have experience with STRs seem more likely to pivot to the MTR strategy once they realize how much easier it is and how well the renters treat their units.