You let the tenant do it and they may cut it once a month when the grass get to about two foot tall.

I realize, this may sound like a tall order.

From what i see they redid the house and it flooded about 17 inches on the house. 

Make sure you clean every square inch of the property really well and take photos when you are done. 

The depth of the filter housing does seem to be about 4 inches so I could see why they would have 2 2-inch filter put in there, but is that the most ideal way, or should I go shopping for some 4 inch filters (if they even make them)?

Put in a new support wall outside, new roof, fixed walk around porch, new HVAC system, 2 new bathrooms done in the historic style in one and not in the other, new water line,  new floors, fixed wall that was fallen 6 inches from second story to foundation, replaced termite damaged foundation beams, paint and cosmetic stuff, all new plumbing, lots more.

Removing the door will give you a a couple of more inches.

Water was a few inches high outside the basement windows during the storm.

If you decide to drywall, look into buying thin 1/4 inch thick drywall and place it right over the paneling.   

Storage of items in or on the premises: Items stored shall be at least twenty-four (24) inches from the heating system and the hot water heater.