Another time someone showed up and spit their gum out on the front lawn before walking up to me.

Alabama is still a place where people know how to Macgyver things & build a house from bubble gum & rubber bands.

I have the 9x9 tiles with the black mastic and was thinking that just covering the tiles with epoxy is the best way to go.

When the house settles the tiles crack and the moisture used in the mastic (sp?)

I'm willing to pay you $1,000 to take out a tooth, adjust my braces because they are cutting my gums, have a filling that just fell out, etc. 

We’re renovating a bathroom and the tenant wanted a surround but whoever installed the shower didn’t use mastic just put the tiles in and pushed them into the wall so gravity has been holding them up for 20 years.

I had renters like that once, and along with being dirty, they got gum stuck in the dryer, nail polish in the carpet, damaged window treatments, burned plastic on the stove, etc.

I think you will regret it when you have to shovel where you live and then shovel your multifamily property or you can buy a snow blower that breaks after your third use or the engine gums up after a season.  

I do the following: plastic sheeting over studs; 30lb felt over that; cement board over that (bottom doesn't touch shower pan or tub by about 1/4" or so); thinset or mastic depending on the tile; caulk all seams.

It's a mostly Section 8 market, but Shirley/Mastic marks the point where the taxes decrease by about 50% from even one town over, making B&H more palatable.