I have a couple buddies that put up 100x40 pole buildings divided into living space, shop and a man cave/bar/collectables section and they love it. They have all kinds of old signs, gas pumps etc. inside and out and seem to be happy as a pig in shit. These guys are both out in the country where they don't have to worry about zoning,and or neighbors. As others have mentioned all the rules of the city and epa might bring you more hassles than you would want to put up with. I did talk to a guy at a swap meet that had bought an old Texaco station that was going to be torn down and was moving it to his lot outside of town. It is his plan to make it his home/ hobby shop, sounds like a good plan to me.