One screening process I found useful was to set up a message line for people to call into on an answering machine.

under the kitchen sink, beside the hot water heater, and near the washing machine.  

Tiff Rent as is, if your biggest complaint there is no washer and dryer, then install the lines and vents DO NOT supply machines.

If you want your BRRRR machine to be perpetual - try for 30% off ARV!

They are still using the washing machine and does not pay water bill.

Regular Hot Tub = No.Hot Tub Time Machine = Yes and be thankful for your good fortune. 

A website could be a 24/7 lead machine.  

I know you feel like you ruled out the washing machine, but I've had an issue where water from the washing machine traveled behind the washer, through a chase space, then into an adjacent closet in my basement. 

If mold is on the joist that would be no problem to clean, just needs some equipment and on the sub floor i believe pending on how severe it is you may just get away with a cleaning with specialized chemical thats stronger than bleach (I know the name but cant remember how its spelled) , as well as a negative air machine, some duct tape, plastic sheething, tyvek suits, gloves and other ppe needed for the workers or it could be severe enough that the floors would have to come up (I know you dont like the sounds of that) and possibly trace it up the walls if any moisture wicked its way up sheetrock and the insulation thats in the walls?...

I don't have a new car, my boat and snow machine while in good shape are not new every year (like theirs are) but mine are paid for, save for the car I own in anchorage.