@Mason MoranThe short answer for the gas station question is to see if all environmental reports where filed timely; if there is any evidence of UST leakage; if the tanks were properly sealed when the station went out of business and the cost of tank removal and any related environmental cleanup.

For example, you can't give a holiday gift to only who you think are good tenants because one of them would post "Thanks Sam for the $25 AMC movies GC my boy friend and I saw Avengers last night xoxo" then your other tenants who didn't get a GC will feel left out.I visit my properties once a month for regular maintenance, mostly for little stuff, like changing AC filters, test smoke alarm batteries, test GFCI receptacles, pour bleach down AC condensate drain lines, exercise water supply stop valves, feel under any drains to check leakage, test water heater T&P valves, etc etc etc...they do not need to be done monthly but that's what I do at each property. 

How might Tulum's infrastructure issues (garbage, sewer leakage) affect its popularity / rentability?  

There is ALWAYS leakage, beaurocracy, and red tape when you give you hard earned money to the government.

There was no water leakage in the basement and no humidity at all.

One item that I was curious to ask here is a swag for dealing with a roof leakage (see below) - is this just an easy fix just using sealant + repainting the interior or can be a more expensive item?

@bjornahland Yes, I am concerned with the up keep and having to deal with any possible mechanical or leakage issues.

If the township closed the oil tank pull without a dig, then there was no leakage, but since the tank (whether oil or septic, which is unlikely) was decommissioned and filled with sand that is not proper procedure and does not preclude a leak of oil.

A few issues quickly emerged when the gas company showed up, first the meters were in the basement when they should of been installed outside (legacy issue), second there was a small amount of leakage in the wall where the service came into the basement before the meters.Luckly since the leak was before the meter they took the responsibility of installing a whole new service from the street and putting all the meters outside.

CO detectors don't always go off if you start having some exhaust leakage into the home either.