Has anyone bought a storage building and remolded for a cake shop?
No, but before I did it, I'd make sure the space had temperature and humidity control (or was airtight enough to put it in) and that it was also closed enough to prevent germs, dust and critters from coming in through the cracks. Then I'd check both the storage facility's policy and any local business regulations and health codes relating to operating a business out of a place like that (that sounds disparaging and I don't mean it to be - if everything is okay with everybody, it sounds like a good idea to me). Let us know if you find out you can do it. It might be the solution to a lot of our space rental problems. Oh, it just occurred to me that you might mean to buy a storage shed for your backyard. If that's the case, most of these considerations still apply, but you might be able to satisfy any local requirements about having a commercial kitchen separate from your home kitchen. I hope you hear from someone who's done this before long!