We've hired out electrical panel upgrades, new plumbing install (for a new laundry room, so all new including drain lines), and countertop install.  

Ours was the shower valve connection behind the shower wall, the water seeped between the shower wall and behind the tub faucet area , and then and drained toward the toilet area, only when the shower head was used. it was hard to track .So might not be the toilet.. we thought that also was our first go round.. 

I sent someone with an hour an had them to cut off the water to the heater and they also drained the water from the heater.  

everyone so far appears to be against the paint option, what I have found from my experience is you can paint metal tubs with no problem as long as you remove the drain and paint under it when reinstall it, if they tape around it which most of them do, it will begin to peel from there, what I would like to know is what is the best cleaning chemical to remove the stain, as far as painting a fiberglass tub I have no experience with that, hope this helps. let us know what you end up doing because I also hate spending money I don't have to.

Multiple income streams is a great thing.Don't tie yourself to a spouse/SO who is a huge drain on your emotional energy or financial energy.

The system they're describing is know as a French drain system.

I would obviously need water lines, gas, grease trap, 25-30 ft of hood space, 2 restrooms, a full kitchen area with drains, a full bar with beer lines, coolers, etc.

As far as drains go, install hair catchers and advise that all plumbing issues that are tenants fault (such as hair, grease etc) are repaired and billed to the tenant.

However, if there is an issue with the road drains etc then they should come help.

She was probably drunk or occupied doing something else stupid and forgot she had the faucet on that fast.I'd charge her every dime for the damage caused, the plumber will verify if the drain and overflow is working, so unless that's clogged or broken pipe which I DOUBT>>>!!!!