Where do you park if you have an SUV and the cost of parking?
Just don't take such a large car into Key West it would be plainly foolish. The roads are narrow and a bit packed and parking is at a real premium. We researched this very question before we went and thus rented the absolutely smallest car available and were very glad we did. Even super compacts are tight on parking in Key West.
If it's a smaller SUV (CRV / Rav 4) you can fit in the lot at the hotel, but you'll need to call ahead to reserve a spot. A suburban or Escalade sized vehicle, you'll probably have to park in a public lot (there is on a few blocks away on Duvel).
Get an answer from Casa 325 staff and past guests.