There are different methods many of us snowbirders use to look for lodging or a campground while going to/from. You can always ask the question as you have done or you can do a little research on your own since most folks won't be traveling the exact route you're going.
Here's what I have done.
--Determine how long I plan to drive the first day. Estimate your average speed (including fueling, potty, food stops). Take the number of hours times the average speed and you'll come up with an approximate location(s) where you might want to get a motel/campground. I move along pretty well on the road, but my average speed is usually around 50-55 mph barring any unforeseen traffic problems.
--There is a nice book called NEXT EXIT. You might want to invest in this book (about $15) as it will be real informative in regard to what motels, fueling locations, food, etc. you'll find at specific exit numbers on all Interstate highways.
--I've also used Google maps to identify what might be available in regard to motels at certain exits. Using these satellite maps you can often see parking areas around motels. You can also phone ahead to motels you find on the Internet to ask about RV parking. We've rarely had problems with parking, but usually we only spend one night in a motel on our way to FL because the 2nd night we're usually in warmer temps and can dewinterize.
We go the I-69/I-65 route (and catch US231 in Montgomery, AL). We've stayed in Bowling Green, KY (exit #22 I believe) where there is a Quality Inn with plenty of parking. Last year we stayed in Brentwood, TN and then this year we made it about 10 miles into AL before we stopped for the night. I think these were all Quality Inns.
Hope this helps some. Good luck with your trip.