Defiantly do the routine screening of the students in addition to the full screening of co-signer including the full credit /background check.Based on the description of the tenant issues you had and the fact that they were students I would suggest that you did not fulfill your responsibilities as a landlord.

Just in case.Now, if it just so happened that the five you liked best were of 5 different races, different sexual orientations, some had kids, LOL, you'd probably be fine.  

I would add that you should find an attorney for your team to review your contracts sooner than later in your investing career, and they may be able to further explain the ramifications of a tenant not fulfilling their end of the rental agreement.

You need to make sure she's on the same page as you, financially, spiritually, sexually, etc before you seriously consider letting her encroach on your single man-space permanently.  

Are you on the sexual offender's list? 

Also, some people prefer to have a mailing address that is not at their home.About your expectation that your "pool of applicants is probably predisposed to having issues with lower income and paying rent late", you are creating a self-fulfilling prophecy.

Here is the Seattle definition: “Discrimination” means any conduct, whether by single act or as part of a practice, the effect of which is to adversely affect or differentiate between or among individuals or groups of individuals, because of race, color, creed, religion, ancestry, national origin, age, sex, marital status, parental status, sexual orientation, gender identity, political ideology, honorably discharged veteran or military status, alternative source of income, participation in a Section 8 or other subsidy program, the presence of any disability, or the use of a service animal by a disabled person.

They don't get it, unless they completely fulfill the terms of the agreement without problems.  

The key is not to discriminate on ethnicity, sex, age, sexual orientation, disability ect. 

This way when a tenant does leave damage should always be minimal and easily covered by their deposit.If you are not doing regular inspections you are not fulfilling your responsibilities of insuring the property is safe and in good repair for your tenant.