I will be going down there in a couple of days, and interested in building/developing/investing, I am a licensed Mexican Architect, I have friends living there as realtors, US investors, and US builders ready to pull the trigger.
From talking to locals, there's a couple of issues than need to be addressed, some are the non-ecological practices that some of those developers have, unfortunately, our government profits from this investors and allows them to destroy manglers (which are the natural water purifying system of that area) dismantling hectares of mangroves and degraded the habitat of resident and migratory species burying animals alive.
There's proof of fecal material floating beneath the city of Tulum, only 20% of the water is sent to the water treatment plant, there's no infrastructure for the exponential growth.
The landfills in the middle of the jungle that is leaking hazardous pollutants into the freshwater system and that something that developers won't tell you.
I love my country and it would be a disaster for everybody if this place ends up like some other great beaches around the world, that are completely ruined by greedy investors not following the rules.
There's no urban or comprehensive master plan, and one of the risks is that Tulum will be like Playa del Carmen is today, overgrown and with environmental devastation.
I will advise doing a lot of research before getting something in Tulum, different country, different rules, and practices.