Been getting nowhere with zoning laws found online and in the local library for Yonkers (in westchester county) as to whether any permits are needed in order to operate such a business. 

I am seeing quotes around $120k which would put that cost per square foot around $600 which seems a lot compared to what I have seen/read online The reason your cost per square foot is so high is you still have to add all the things a regular house has but in a smaller space.

When talking to property managers, ask questions regarding any guarantees they offer owners and refer to any online reviews to get a better idea of how tenants and other owners feel about working with the company.

Quickbooks online could work for what you need.  

A lot of that is referral based or people find my site online, organically. 

Luckily I was in a buyer's market at the time, but about 75% of agents did not even respond to me and I could not set up appointments online because I was not a MLS member.   

David, are your credit literacy and other presentations posted somewhere online?

If there are barriers that limit similar supply and you figure out how to get the housing units online, even better. 

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.

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