They did, in fact, provide a money-back guarantee if it did not outperform the market in a one-mile radius, which in my case is a really well-performing area that is borderline saturated.

I go back to see what I sent them and I had fat fingered an address (389 instead of 380).  

How much "fat" do you believe still exists within that? 

I guess my main concern with the Tulum area is it seems there are soooo many new developments going in (an agent told me 151 new developments over the next 4 or 5 years), I think the competition for vacation rentals will end up like Playa del Carmen (saturated and cut-throat with competition).

STR would be another option, but a lot of markets are saturated, so you must do your research.

Is the market saturated?

Marketing material from commercial brokers in all 50 states, for all sorts of NNN, isn't useful, and you aren't going to really get insights until you narrow your focus a bit.Starbuck is a nice easy thing to watch b/c they are all over and, since Americans have largely replaced their trans fat addition (McDonalds, Burger King) with a sugary caffeine addition (Starbucks), it's likely going to do well for a few decades. 

The market is saturated with STR's further from the beach and attractions, so my advice is to be picky about your location and underwrite the numbers carefully to make sure the investment will be profitable. 

Like ODC that has a portion of their deals that never really returned anything and were sent letters saying they needed a capital call or were going to take a big fat hair cut.. then ODC decided in the best interest of the company and investors to bring in pref equity according to what has been posted thereby diluting the original investors..

Some investors make it work by targeting less saturated areas nearby, but a lot of folks find more affordable markets out of state, which can make this strategy more feasible.Capital needs can vary quite a bit depending on factors like partnering, financing options, and property types.