In all honesty.... don't - incredibly hard to make any money while being ethical to the fish.
But generally speaking the "path" so to speak starts with a large collection at home, a fish house with breeding set ups which enable you to make a little money from this, then when you have a little circle of suppliers and know you can get all your goods together - thats when I think a shop would be feasable. I think I read somewhere that on average a small independant shops turn over £50 - £75k but massive overheads with water, dechlorinator and equipment. That said Maidenhead in the UK is a franchise I believe so that must be capable of £250k + other wise it would not be worth investors time and capital.
The other thing to think about is the massive cost of getting set up - you would be leasing a shop for one and in the start while you are building stock and cycling filters you would have at least a months rent that would need covering with 0 sales. And then there is all the tanks and equipment - heaters etc. You would need to decide how to filter all the tanks, would you do one massive pond filter for the whole shop or racks with a sump or individual filters in each tank.
I think the biggest mistake for a lot of fish shops is that they are often in the middle of nowhere - in a random house in a random street in a random town outside of a city or in the middle of an industrial estate.... Which is great for enthusiasts who want to hunt out the shop but what is never going to happen is for a passing family who are thinking of a fish tank to walk in and get hooked on the hobby, who then buy a tank and equipment.
The hardest part to make money on now is probably the equipment because there are so many competitive places now online who dont have the running costs of a shop.
One trick I have seen in the UK is - sell your bread and butter fish and some rarer smaller fish as cheap as you can and then when you get your high end fish like big Panaques and other Plecs get the prices up - there is a shop in the UK (some people will guess) charging £700 for some plecs that in other shops Ive been told could sell for £150 and they are selling them! But the thing is until I found this out I just trusted them on price because of the cheap bread and butter fish and schooling fish - not that I got one of the mega expensive plecs but what that shows is its a bit of faith in a store that makes the money. There is an other shop in my home town that sells fish mega expensive but he has a lot of regular customers and not a lot of competitors in the city which means he charges what he likes - often 2 to 3 times more than a store on the outskirts of the city.
Wills