I have been very fortunate on this side.Also, setting it up more friendly for business travelers (like documenting fast wifi upload/download speeds, having a good desk space, possibly wired internet also, an inexpensive printer, etc.)

I rented to smart working young people who rented something inexpensive, while they saved up to buy their first home.  

As for me, I would require liability coverage of 500K or more.....To go from one liability level to the a higher one is very inexpensive.......and remember, this is what protects them as well as you.If you feel strongly enough about it and don't want to take the chance the renter will flake on this down the road, then build the cost of the policy into the rents.

It saved me bunches, so if I were you I would just keep my eye out and when you see a inexpensive unit get it for a back up .

I run the  courts through small claims court which is inexpensive and usually do collect although it is sometimes years later when they need to clear their credit report.Small claims court is simple to do yourself and usually worth the effort.

It's a really inexpensive setup and works very well.

Four units would cost you $4,800/month in expenses? 

What is your last years increase in expenses? 

Very inexpensive and they set up in minutes.

Your goal should be to rid yourself of this tenant, ASAP, as quickly and as inexpensively as possible.