I was thinking that they get paid the most when there is turnover, so has anyone been successful in crafting an agreement that rewards for:Tenant longevityShort vacancyKeeping repair costs down (I do want to address issues though)Dunno...

DFW is growing and it all hinges on when/if that growth will stop.2017 DFW added 32,000 new rental units (Source)From June 2017 to June 2018 35,000 new homes starts (Source)2018 DFW has issued 19,000 new permits for rental unit construction (Source)The last of these sources from Texas A&M gives some great detail on market absorption of the new units and demand/vacancy rates.

Did you then send a demand letter itemized as to what is owed to you to the tenant at their last known address?

But your detail of the scenario has cleared things up, and has actually helped to understand the whole process much better.

Here's what I would do if I was in your situation:Google the property address and unit and see if any rental listings come up.

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

If you have questions on that let me know and I can go into more details. 

I don't know any details on your rents, costs, area, NOI or any other details, so not weighing in if you should buy or not. 

In other words, if they have no proof, but you do, then you win as most states have landlord/tenant law that favors the tenant.As was stated above, keep your small claims court date and be prepared to take your proof, as well as a VERY detailed account of everything you can remember from conversations and other occurrences between you and the landlord, or the landlord's rep, to court with you.In Colorado, for example, the landlord must return the deposit in full, or issue a check and a detailed statement covering the amounts not returned, within 30 days. 

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.