All your properties may be perfect but if you are transparent about why something is not in service, it makes sense, and they agree it works just fine for long-term rentals.

If you're focused on medical travel folks, smaller 1 or 2 bed properties work fine.

(most hard money loans require 10-15% down depending on the split between purchase price and rehab). but that is both (1) risky and (2) expensive, as you're paying interest every month on 100% of the borrowed funds. private money is fine, you're just bearing a lot of risk and also involving the relationship in your very first deal. 

Do I have to give a tenant a written notice to vacate the unit upon lease end or is a text message fine?

The only issue with seller finance and resale is if they don't want to receive a payoff in short order, then they should include a pre-payment penalty. 

These accountants believe that purchasing from a related party is fine as long as it is an arms- length documented market-consistent transaction.   

Send a certified letter today so you can prove that they received it.

Regarding the advice you've received from others, the best thing to do is to learn your market. 

I do not work for Stessa in any capacity and I don't receive anything from referring them.

I noticed on the city website that it can only be done in certain areas, which I'm more than fine with.