A bit biased but Awning is awesome, not only is there the free Awning Airbnb Estimator, but you can also navigate to Top Deals, which are pre-analyzed STR and LTR deals across the country.

Biased, but realtor.

The question: are there common trends in personality type, age, occupation, gender, etc. of the people who let you sell their properties?

Following law school, I went into estate planning and asset protection, so I may be biased when I say this, but not all attorneys and CPAs are created equal. 

I live in Pittsburgh, so biased but own businesses in Cleveland market too.

Seems a bit biased to have a singular option, right?

Great, rent to one of the other 190 that do as you request without fighting you on it... self selection bias is a thing of beauty, you're narrowing your pool to people that you're more likely to want as tenants anyways. 

Have a bias towards building capital and experience.  

The market has an upward bias but is generally cyclical. 

If there is a limited number of buyers or the financing is bias towards those with a large down payment you will see the value lag.John CoreyPS.