I bought one for my last house. We already had a concrete driveway, so the base was alreay there.
The one I bought, from Argos, was the biggest Yardmaster. I think it was 16' x 9', the one with the car inside in the catelog.
No problem to assemble, just read the instructions a few times first, to get the overall assembly sequence, then assembled the panels on my own (with the instructions) , and an electric screwdriver. Finally, two of us did the final assembly. Total assembly was done over a weekend.
I then wired it for lights and power, and used 35mm builders-type aeroboard to insulate it. This slotted nicely between the panel uprights. We also secured it to the concrete base using coach bolts, and ran a bead of silicone around the base.
It was still there 5 years later when we sold the house, the shed was looking good as new.
OK, so it took a weekend to assemble the shed, but at a total cost of £799 at the time to purchase, it was far cheaper than any other option, including wooden shed. And it was maintenance free.