Pay for the extra detailed one that does nationwide criminal records check(this doesn't necessarily get all of them) and evictions.Always exhaust every financially reasonable solution to avoid having to evict or sue somebody.Always raise the rent every year, even if only $25, unless you think it will take 2-3 months to retenant because of so much available inventory in your area.Actually I almost forgot the most important one.

Illegal is a term implying a criminal action.

There are also drug dealers and criminals in these areas. 

Unless of course there is some egregious gross negligence AND you have other assets of high value they can come after, they usually will not waste their time and you would be more likely involved in a criminal suit to which the civil suit would be the least of your worries.   

Same goes for criminal records and credit check.2.

It’s not in a bad criminal neighborhood, but it’s not on the best side of town either.

Also, who knows what will happen in the future as one of them might move out for some reason.2) If you use a free online application then most of the time they do charge fees - visit the landlord resources tab on BP under tools and then services so you can see some free options. 3) I would do all of these things in the list - once again, if you use an online criminal background check and credit report then they will hit all of these things!

Just a few additional thoughts - Run a background check that includes credit history and criminal background.

It was a criminal complaint against me. 

BA in Criminal Justice & MA in Urban Affairs (urban planning/ public policy).