As an investor, you'll need to wait until this period expires before your offer will be considered.Additionally, Freddie Mac may require proof of funds or a pre-approval letter with your offer, and they often prefer cash offers or conventional financing.

Get copies of the lease and proof that they are paying on time and yes get an estoppel certificate. 

Also, if you have cash to complete the purchase, you can get preapproved and then make an offer with proof of funds and without a financing contingency with a standard 30 days to close.

I figure the upside to the rental scenario is, of course, investing in multiple properties, while a downside would be having to most likely get a conventional loan on the second house with 20+% down and proof of sufficient enough financial reserves to handle two mortgages. 

Obtaining valid ID and proof of income isn’t hard; for buyer prospects, swap proof of income for a pre-approval letter and/or proof of funds.

Jordan,The burden of proof will be on you (your attorney) if you sue your neighbor.

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.

There's no proof it's even bottomed yet. 

No, just inform them you are the new owner (they may want proof) and provide them with the address to send payments. 

I just bought all the drywall, cement board, and a 3/4 full thing of red guard water proofing that I need for my entire bathroom remodel for no joke $110, that would have cost me $400+ at the store but someone else who already finished their bathroom just had a ton left over.