I haven't been involved in the beginnings of a tea shop, but I do know of a couple places that started as small as they could probably afford. One in particular (since I've actually spoken to the owner of that shop) basically emphasized the location he was in and the quality/variety of tea he carried, and word-of-mouth carried him until he'd made enough to completely remodel the place, actually add a decent kitchen (they now have a lunch menu and a Sunday brunch), add a couple more varieties of tea as well as a smallish selection of teawares, and hire more help. He's still in the same location, serving mostly the same tea in mostly the same way, but the business has grown to more than just he and his wife - now I rarely see him in there (not that I go all that often anymore, since I've moved).
I go back every chance I get - yes, it looked a little drab and like a hole-in-the-wall the first time I went in. But it was the tea that brought me back, and I'm very glad to see he's doing well.