(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. 

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

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. 

We receive weekly reporting from our third-party vendor on filter deliveries, and have very few errors. 

If you can get a better deal on the home due to age its a fine and if you need financing banks do not judge year built. 

- Do you want an ocean view, or is proximity to the water or to resort amenities like fine dining or shops most important?

I don't quite understand why you need to rewrite the lease, it seems to me that what as Nathan said, just adding to the existing lease should be fine

My question is this - does Johnson City receive enough visitation to justify a successful STR?

Right now I'm over $100 than I wanted but that's fine because once I rent it out fully I know I can cash flow about $500 or more.

@Troy SmithThe advice you received is correct.