While it is very difficult to collect on a judgement in Texas, your sister has a good chance to collect someday as the property is most likely non-exempt

Background/credit check, income verification, talk to their boss, talk to their last two landlords, collect a security deposit, etc. 2.)

@Don Thornton does your contract state you pay monthly flat fees, fees based on rent collection or whichever is higher?

Haha....ok I'm joking, kind of...All those things are important, but first is credit score(700 or better preferred, can go lower if other conditions are optimal) and no previous evictions, no felony convictions(especially violent or sexual).

As I write this, I have 3 late rents to collect of my 10 doors.

Property specific software like TenantCloud or Cozy would help with rent collection.

However, don't think just selling a list of names and numbers is necessarily a referral and you may be able to collect compensation for that (or, more accurately, you may find an agent who is willing to do that).  

When you can eventually get renters in the other units, you will be collecting rent payments from them which will offset your monthly mortgage expense. 

@Anthony Murphy PM's base their pricing on gross rent typically so they collect it, take their cut plus expenses and send you the rest.

I am unsure if I should list it on as many sites as possible to optimize occupancy rate.