I'd do both racks and cages.
And I appreciate the input from all of you, this is definitley giving me something to think about... I think my market would definitely be snake owners such as myselves, ones with only a few snakes and who are relatively new to keeping them.
Also, I'd build the cages for whichever type of animal the customer has. With a little modification, the rabbit hutch I'm building could easily be used to hold snakes.