Have you already used a source to estimate the STR income?  

There's a very good chance the issue(s) you face have already been discussed and answered.Ask questions in the appropriate forum.

If you are targeting small multifamily properties, that statement can be true, but if you are targeting larger units, the chances of paying cash are very small to none, as many people will buy it using banks and a mix of syndication, so savvy investors will ignore your letterThe PS section where says " or if they have tenants in the property."

Understand what retails properties sell, average prices per sq/ft, types of properties investors are looking for, what rents are, what areas sell the best for investors, what to look for to get accurate rehab estimates, more properties you visit and see in-person the better, and most importantly, dont be lazy! 

Since you're in Florida and the laws are much more fair, I'd be willing to take a chance if his background/credit check came in clean. 

Then the buyer was paying closing costs, which I estimated around $11,000.

It’s good to run conservative estimates, especially since vacation rentals can be seasonal in some places.If freeing up time is one of your main goals, think about using a property management company.

4) Due to all of the above, high chance they start playing games with other tenants, leading to bigger problems.5) What happens if you have to part ways?

If your purchase price (always the largest expense) plus the rehab estimate (the second largest) total no more than 70% of the ARV, the remaining 30% must cover your HML charges, agent commission, property and hazard insurance, property taxes, title insurance, escrow, staging, all else, and your profit.

I am estimating my home is now worth at minimum 615k but think it could be anywhere from 650-700kMy current mortgage payment is 3324 (that with PMI).