Be brutally honest with yourself about the idea and the market for it - plus the retail market in general. Does this idea really need a physical shop in the current climate, or could you run it solely online? Even if you do want a physical location, could you test the water with Etsy, Amazon Marketplace etc.?
If your idea is fabulous, why has no one else had it? This isn’t me trying to say ‘Obviously it can’t be that fabulous’ or anything similarly sarcastic by the way
It’s a genuine question. Is it a genuinely unique idea? Or is it an idea others have looked at and thought ‘There’s a market for this, but it’s not enough to build a business on’? Or it could be that similar businesses exist elsewhere, but that it’s not the right concept for your location. The artisan breads and customised cupcakes that will sell in Ealing, Harborne or Hale won’t make you much money in Edmonton, Lozells or Moss Side. If you’re going to go to the expensive of a bricks and mortar location, choose that location very wisely.
What will you need in the way of staff? Are you planning on being a one-woman band? Can you afford to close up if you need a holiday or time off sick?
Most importantly, what will make what you do unique? Why would a customer pick you and not a competitor? A lot of people take the talk about wanting to use independent shops, but the reality is those shops need something extra to stay competitive ahead of larger retailers, and particularly online retailers.
None of this means you shouldn’t go for it, by the way! But go in with your eyes wide open, in the right location and with realistic expectations.