Require the contractor to use a more mold resistant caulk (than  the 39 cent kind from the Dollar Store).https://thetoiletzone.com/best-shower-caulk-prevent-mildew/

We installed commercial grade mold resistance sheet-rock in both bathrooms as well.

My logic would be the path of least resistance and not fight the city and just MTR the place. 

If they resist, it may be helpful to offer to provide the entire deposit back as soon as they turn over keys if they're up to date on rent and unit is in decent condition rather than make them wait the x days allowed in the landlord/tenant laws. 

Low unemployment, recession-resistant economy because of the federal govt. 

My intention is to become an investor to build wealth and pay off my own and my daughter's student loans as soon as I can, but I am stuck here in Sebastopol, CA until she graduates before I can move, save up enough money, and do the house hack thing, which seems like the path of least resistance to get into the market.

If you are making 3-5K you arent going to have a ton of resistance from a seller when you tell them you wont be the end buyer of the property, but its hard to convince someone that you making a 20K-30K fee is in their best interest.

Whether it's about investing in real estate in Mexico, the US or Canada or it's about stocks or crypto, some people don't seem to be able to resist a story, whether good or bad.

It's more recession resistant as the people who are staying with you are also making money in the area.

The argument is that it is water resistant, not waterproof and that a tile job done with it will have a lifespan of five years or less.