Do some basic market research in the local area of the brick and mortar location. You are looking for the number of outlets already operating and go from there.

There are some places with over saturation in the market place, some markets are still waiting for a dedicated vapors store.

Added: Make sure your potential partner or your employees know the product, perhaps even use it.

We have a few places locally but at the best 1 every one working there gave up cigarettes and now use vapor instead.

Did not hear from you =(