If your tenant has been playing these "schemes" then likely they've done this with the previous landlord and gotten away with it - so I hope you bought the property for a good price in order to account for this potential headache. 

A good attorney, RMLO, and servicing company play a big part of this. .

The borrower's financials play a big part as well.

Play the long game and hold onto that equity. 

NEVER borrow from a 401K, you are taking pre-taxed dollars and paying it back with after tax dollars, you do not get to return the loan with pre taxed dollars, in addition, some 401K plans do charge interest and maybe even fees, and lastly if you get laid off for some reason, it is a distribution with all the "fun consequences: tax at the last dollar rate, and if you are under 59.5 there is also the additional 10% penalty.Personally I like the HELOC, however you can also sell stocks and do tax harvesting there to offset gains if that is an option

Not fun for anyone. 

*As a side note, I think maybe it would be fun also to try and identify where new technology or machine-learning driven approaches could increase efficiency in the spaceAs for my financial situation, personally, I have around 50k saved but 20k of it is tied up in assets I don't want to pay capital gains tax on.

The 2nd group can often be spotted via the credit report, and they are a lot less fun to host (late payments, asking for concessions, demanding, etc.)

Pic for fun.

I recently have connected with investors who are interested in assisted living facilities, with the play of unlocking government funding, not sure if there's similar opportunities with SL facilities.