Install new interior bedroomand closet doors (6 panel doors with hardware).

I know it was unplanned and a  surprise but So is peeling off old shingles and finding rotten wet panels .

You may want to do all the electrical as well with new panel and it may be time for plumbing as well. 

Some ideas I have been teasing around are building a rental storage facility, leasing the land for a solar farm (although the lot may be too small for that), building a multifamily complex, or simply using the land for advertising.

Everything else has to be refreshed : Floors (carpeted, heavily spoiled and cat urine odor) Ceilings dry-wallWalls dry-wallElectrical is out of date (knot and tube all over, electrical panel needs replacement) Risks: Sanitization (cat urine smell, potential for pest problems)Structural integrity not checked (unable to check in a timely fashion due to deadline)Evidence of water damage on main floor ceiling, extent of damages unknownNo smell of mold in basement but knowing the city history of flooding, this is uncertainPlumbing looks recent but it was hard to be absolutely sure of this assertionThe reason I decided against in the end : too many unknowns.

If we do, then we need to upgrade 3 panels and meter sockets, which I have a bid for at 6k. 

The extremely damp conditions will infiltrate to the unit/s above and will drastically reduce the useful life of everything in the bsmnt. incl. the water heater, furnace, electrical panel, etc.

It turns out that the landowner who I called back, owned another piece of land that did meet my specs for a solar project and it was well worth the callback.It does not have to be at the top of your list but I always think it's worth talking to landowners.

They have now forwarded it to the Appraisal manager with the Appraisal company, who is having a panel of appraisers take a look.  

You will need 1 for each unit and wire them into each units electrical panel (you could use actuators and power a single pump off 1 electrical source).