My questions are:- is it worth investing there in terms of the safety of tenants?

Taking legal action against another party necessarily involves questions of law and can result detrimental legal impacts on him if he files a lawsuit without proper grounds to do so, or where the opposing party may have counter-claims against him.

It is free to you and costs the tenants $35 to run their credit.Depending on your state make sure you understand the laws around discrimination.

And in many cases this may be warranted as health and safety issues may be present.  

Our state law states "An owner may impose a reasonablelate fee for each month an occupant does not pay rent when due."

The difference between a safety line and a safety net is that a safety net (your words) can break one line and still hold a fish. 

We are finishing up some renovations on a house with an in-law on Cape Cod.

Sure there is a very small chance that something will go wrong, but with the tightening rental laws spending a little on a proper lease is smart.

I just got off the phone with a law firm doing the foreclosure legal work for a bank.

Regardless, the tax law is hundreds of pages and only 5% tells us to pay taxes, the other 95% tells us how to not pay taxes.