I don't own a store, but before looking at expenses I would look at customers in your area. Do a survey or something of the likes to check out wether or not you could build a sustainable customer base to cover the expenses. Ask potential customers to your "to be" store what they want to see, what they want to buy and what they are willing to spend. How many people in the area you are in are actually looking for a more specialized lfs? Without customers willing to go to your store and spend their hard earned cash, the question of expenses become moot...
Keep in mind the bad economy, the costs of running a store; as in rent/mortgage on the property, electricity costs for the tanks, water costs for the tanks ( I don't know how it works in the USA, but in holland we have to pay for the water coming in as well as the water going out!) are you going to supply the fish from your own breeding stock or will you need to find a wholesaler or several different breeders to supply you with the fish? Will you only sell fish or tanks and other necessities as well?
The costs of opening a shop is probably the last thing you should worry about. Figure everything else out first, then IF you have a viable location, business plan and potential costumer base worry about the start up costs. Once you have figured that out you could probably (again, in holland banks have special loans for first time business owners) get a loan from the bank, but make sure you have a great business plan to show them the viability of your store!
I hope this helps a bit in making your idea reality! And good Luck!!
