All adults know where they can push the limits. 

Totally agree on not babysitting adults.

I consider myself to be very lucky because I bought early and I did not read any rei books.Yes many can say that ...my hs econ teacher back in 1999 would tell us how stupid his brother was and how he even did an adult film because that's the type of low life.  

I fully screen every adult applicant and have every applicant on the lease to make my ability to collect in the event of a default more secure.

But, remember, they are going to be capable adults who could do what you have done or are doing.  

I limit to two unrelated adults for even three or four bedroom houses.

I had my last rental for next school year get rented this week, and I took a group of young adults that weren't in school over students to hedge against the unknown, like you are referring to.

If they have low credit and no reserves, I’d only rent to them if there are two or more working adults in the home.

We each have to make that decision for ourselves as adults. 

I have been working in analytical fields for all of my adult live (pension actuarial student and IT/management consultant), and am looking at other ways of providing residual income for myself and my family.Thank you for taking the time to read my introduction.