Both cities just enacted some rent control legislation you'll want to make yourself aware of, and there's plenty of good forums going around BP about that. 

I generally don't like the idea of borrowing against a 401(k) for any reason mainly because of risk that the loan will be called due to something outside of your control like losing your job. 

Just get control like you you were thinking is my bad advice.  

And just general rent control.

I have a Solo 401K with checkbook control for the master account.

I agree, but if someone is a KP and signing on to the loan they would want some control in deal to make sure the deal doesn't go under and ruin their credit.

The unit itself worked well for temperature control.

That means mowing your yard, cleaning up leaves and controlling weeds.

I've been investing in real estate for a while and often become frustrated with the process and I end up trying to control everything.   

I imagine having to train someone up who wants to do this themselves... high level of quality control required.