For a few weeks in the spring & fall major car rental companies need to move their fleets north or south to meet seasonal demand. During these times they offer pretty inexpensive one way rates and no drop off fees with special codes to and from major cities. Orlando is one of these, your home town or area may be one of the northern points they offer. They move cars south in the fall and to the north in the spring.
Outside of these weeks and cities a car rental drop off in a distant location will be $$$$$. There is either a high drop fee since you are dropping it off out of the state of origin, or no drop fee but a "special" (read inflated) one way rate. After 9/11 rental companies waived drop fees since people couldn't fly home, but that's an isolated event.
It's certainly possible to drive one way and fly the other, but in a rental car it will cost considerably more unless you get one of the fleet moving deals. Since you're posting from AL, I don't think these deals would apply. It applies mostly to the NYC, Boston, Philly, etc. areas. The only way to know for sure is to price it out.