You don’t need a degree to open a store. You do need some other things, such as a business license, a business plan, and funding. But if you’re talking about “for profit,” it’s not lending—it’s renting. And if it’s a store, it’s not a library at all. It might be a good idea first to look for a part-time job in a store like that near you, or volunteer in a nonprofit used-goods outlet, to see how you like the work. (Also you can have a master’s or other degree and still be a private citizen.)