A flipper I know didn't follow his recommendation and applied Killz (water based in CA) and during Realtor walk through, prospective buyers complained of cig smell.

You need 2 hvac systems , 2 electric meters , you should split the units and submeter the water .   

For example, a hot water heater is ready to go versus a bathroom you want to upgrade.

We have had two different contractors try to fix using various types of cement/epoxy while digging up outside area and they can not seem to get it right but have decreased the water a bit.

Water/sewer sent water usage and it was 2 to 3,000 gallons used every day for the month of April.  

Certainly replacing a furnace and/or a water heater would require a permit as well as running a new or replacing a duct run.

For example, if a family is displaced due to extensive water damage that will take a few months to repair, the insurance company will then look to find temporary housing for their customer/displaced family.

We are leaning towards testing the waters for putting it on the market even though originally it was going to be a long term buy and hold.

I believe that the shower in the second floor bathroom is causing water damage and creating the mold in the first floor bathroom ceiling, which may require removing the first floor bathroom ceiling. 

Water, air, sewage?