I'd estimate about half of the time he's here I couldn't use the bathroom.

From that point forward I was on the lookout for a 3 Bedroom, 1 Bathroom, Ranch with a 2 car garage in a hard working neighborhood.

I found this on the county website, listed under the house's address: "EXISTING SCREEN ROOM 10X14 W/ ACRCYLIC WINDOWS EXTEND EXISTING SLAB TO REAR OF SFR" I'm wondering if only the extra bathroom is unpermitted?

After visiting the property for second time I found out that the upper floor has kind of curvature in the bathroom area.

that's because u aren't listed on mls. do a search for homes for rent in your area that match your property's description (bedrooms/bathrooms, zipcode, etc) and see what others are listed for.

I'm installing it in the kitchen/bathrooms on my latest rental.

The things to watch with forced air, from my own experience with this would include: Are there good returns (and no returns from bathroom)?

I've tried the frosting in a spray can that is supposedly meant for a bathroom, but it was worthless.

They will splash water out of the tub into the bathroom floor.

Installation of one or two interior doors, one from the bedroom, one from the bath, to another (the same)room, water timer added to shower plumbing, as well maybe as heater for that bathroom, and possibly some outside outlets for use near a pool, building a soundproof box to house these darn noisy refrigerators and provide some pantry space in kitchen.