Assuming that a loan required 10% down, how do people come up with the 10% when going from seller financing to traditional financing? 

While it's unlikely that all burners will be used simultaneously, I want to ensure proper ventilation in case tenants decide to cook large meals regularly.The standard rule suggests dividing the BTU by 100 to determine the required CFM for the vent hood.

Are there certain market/demographic requirements you look for with tiny house projects?  

I'm all for stricter requirements to become an agent.

(Bonus) Have at least 2 (two) local handypeople on call for regular maintenance and emergency calls.   

Some states require you to store it for 30 days. 

When you get the wholesale buyer, you should require they put up an equal or higher deposit.

I would save half of the rent for repairs, vacancy and general maintenance.

That's what I would use in MD, BUT not sure if there are specific requirements in Oklahoma City.

It's 10% of income the tenant pays, I believe, so they should meet your income requirement by virtue of holding the voucher.