This is a vacation spot that I normally visit several times a year and the short term rental income will help offset the costs. 

A good way to do this is have it electronically signed the night before you meet with them to exchange money.

I have been researching everything to do with real estate investing for the past several years and am finally getting to a spot I can start to actually invest.

These spots have been getting more attention from investors and can offer solid cash flow while still being in communities that are seeing improvements.

I know this isn't the usual STR approach as most are going after high end vacation spots, etc but to me this strategy is low risk as I'll make sure the numbers work so that I can convert to LTR if needed. 

I don't think you've been 100% right, nor have the more vocal detractors been spot on with everything either.I advise that you don't give up on MTR as a strategy, if it appeals to you.

I can easily come up with the remainder needed to finish off the mortgage, however, that leaves me in a bit of an undesirable spot.

The biggest detractor is limited control and timing of exit.Regarding your low debt position today, it puts you in an odd spot with DSTs that have either no debt or 50+% LTV. 

Once you've built up some reserves or feel like you're in a good spot, you could switch gears to MTR, especially since you're so close to a hospital.And later on, you might even mix it up between MTR and short-term rentals (STR), depending on demand.

However, do make sure you have some form of electronic confirmation that their payment was received.