Went with this one at Home Depot; will run you about $600. Total PIA to assemble. Definitely use a rubber mallet and loads of liquid dish soap on the joints to ease things along. Read the reviews. The last panel, a roof panel, is a total b*tch to assemble. My "helper" (aka "wife"

threw up her hands and went inside, leaving me cussing on a step-ladder.
Had it in place for three years in a north Texas back yard. Held up amazingly well in the heat and freezing cold; never leaked. Plenty of room inside. Most expensive part was outfitting the walls with the specialized hangers sold at Home Depot. The walls are thin but rigid, and they require special hangers to hold yard tools, trimmers, etc. Them hangers ain't cheap.
Would buy this again in a heartbeat, but would bribe a buddy with beer to help me assemble it this time. Put ours on a bed of levelled coarse gravel. Here's a description, below, but again...ignore the BS about it being easy to put together. It ain't.
"Rubbermaid Big Max 7 Ft. x 7 Ft. Plastic Storage Shed
Model # FG5H80000SDONX
Internet # 202046941"
Easy to assemble with 325 cubic feet of
storage capacity, the design of the new Big Max compliments your home and yard. Its double-walled construction provides extra protection for items stored inside. Durable, all-weather resin ensures no rot, no rust, no problems. Our new wall anchor system allows easy installation of shelving, pegboard and other accessories.
Storage Capacity: 325 cubic feet
Inside Dimensions: 6 ft. 9 in. w x 6 ft. 9 in. d x 7 ft. 7.5 in.h
Durable: leak-resistant, dent-resistant, weather-resistant
Maintenance Free: no rot, no rust, no problems
Easy to assemble; Heavy duty, impact resistant floor included
Lockable doors - Secure your belongings (lock not included)
Includes two skylights, two front windows and wide double door entry
Review state and local building codes prior to assembly
Heavy duty, impact resistant floor included
MFG Brand Name : Rubbermaid
MFG Model # : FG5H80000SDONX
MFG Part # : FG5H80000SDONX