You would only pay taxes on all passive investments in a traditional SDIRA at distribution, unless you have a mortgage, then the portion of the income derived because of the mortgage will be subject to UDFI (unrelated debt finance income) which will trigger UBIT (unrelated business income tax). 

If you can find that deal, pull that trigger.

Dig into reverse mortgages before pulling the trigger on anything, specifically HECM's (FHA product).

You have three choices...transfer the property and keep the loan in tact hoping they won't trigger due on sale, refinance into a loan that allows it, or simply leave things as they are. 

But if they don't willingly make the payment your only option would be to sue, and they have the upper hand to let the lender know about the sale possibly triggering DOS.

Selling would likely trigger capital gains taxes (unless you lived in the property for two out of the last five years or use a 1031 exchange).

I made poor judgment when I was younger because I was too quick to pull the trigger on some things.

If the mortgage is in trouble that would trigger a foreclosure.

The underlying note from the lender is still in place and the Due On Sale can be triggered.

There are often automated flags that will be triggered if you do it, so it's best just to know how they will react.