I find it a bit strange that someone who isn't clued up, should open a shop selling something they don't know much about ????
But....I'd suggest buying in a whole pile of goods and using them yourself....That way, you have the experience and knowledge to keep your customers informed of what they're buying and can give practical informed advice....A lot of people who visit B+M stores are first time buyers and can be put off by the sheer choice of products on sale, not to mention the more experienced vapers who will probably never come back as regular customers if they they think the vendor doesn't have a clue about what they're selling.
Just my opinion of course.......