Expect them to be expensive, also.  

To make taxes easier we set up a business checking account and had all the rent paid into that account and all the expenses paid out of that account.

It's simple enough to make a row for income, and another for expenses, and then subdivide those expenses, and add them up in the total expenses cell and then subtract the gross income from those total expenses to get my net.

My Ex-wife currently lives in my fathers home.

Too expensive.

@Eric Coats, to answer your specific questions, estimating expenses are pretty simple. 

The brother and his son had been living in the house, free of charge, for years, and were gaming the system.

IF you plan on going back someday, and this is the home you want to move back to, then renting it would be a good idea as long as you estimate that it will cover itself, or preferably, cash flow, which it appears that yours will at @ $2K or so per month (after expenses). 

As a Mexican real estate agent living in Canada and with a presence in the United States, one of the most common questions I hear in the investor community is: "Can foreigners buy real estate in Mexico?"

Quote from @Matthew Irish-Jones: Quote from @Mark Cruse: Yes, there will be more expenses above what's mentioned here but if this is done properly it can be kept to a minimum.