major rv parking structure in san diego area
What is driving this demand? What will rising fuel prices do to the demand?
Multi-level? Keep in mind that (some) RVs are heavy (over 18 tons), tall (14 feet or even more with antennas), wide (8 1/2 feet) and long (over 40 feet). The bigger ones take a lot of space to maneuver. So, you might want to have the bottom floor for the big motorhomes, the next floor for the littler motorhomes, and the top floor for trailers (pull through parking spaces so people don't have to back in).
Is it going to be completely enclosed or open like a parking garage? Secure access, automated or manned?
You might want to offer the option of plugging in electrical (15 amps should be adequate) to keep batteries maintained/humidifier going (long term storage) or the fridge going (short term storage). It would be nice if your lighting would power the solar cells of the units which have them.
You might want to have a couple of 'prep bays' where people could dump sewage, fill water tanks, test all the other hookups (water/electrical/cable/possibly phone) and wash the unit before or after a trip, including awnings. Possibly even service bays where they could change oil/lube the unit, although this might be an insurance problem. Alternatively, you might offer basic maintenance services.