Each of you are putting in half of the down payment, but I'd consider agreeing to a 60/40 split of the net income in favor of them. 

A direct booking site still has to process a credit card payment.

Because of the protections an LLC offers in this space, I'd simply say my non-expert opinion would be to spend a little extra to make a separate LLC for this new home, for the legal protections & to make your taxes less of a headache for you.

They didn’t go as strict as they threatened, at least not yet…https://www.atlantaga.gov/government/departments/city-planni...2 properties maximum and the first one must be  your primary home… so be prepared to move there and pay state income taxes  https://www.atlantaga.gov/home/showpublisheddocument/54610/6...you and your landlord will have to get this form notarized.Please just make sure you have a plan to keep making rent payments after your short term rental plans are banned.  

Ask for a down payment that you can then take to invest elsewhere and then you will also still be receiving monthly cash flow coming in on the seller finance payments.

Definitely something to consider when looking in addition to understanding if it is warrantable or non-warrantable and limitations as such. 

If you do 80% LTV on a $220,000 purchase price that gives you a $1,216 monthly payment. 

.** (Isn't that what making monthly payments on seller buyback is?)

I'm a RE Agent and Investor in central Houston (one of our houses is up in Spring) and I use Hemlane.com to track and manage payments, maintenance requests, ect. 

@Steven Wocknitz It's more common in Canada to call hard money lenders B lenders or non-banks.