And let her know that since you have not received the property back from her, you will evict her and her rifraf once the courts are open for eviction and it will go on all their records, and you will haunt her for the rest of her life keeping the unpaid rent as a collection on her credit report until she pays it. 

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?

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.

Second, "nearly a third" implies that normal is 100% of rent collections.