well David the members who have posted don't have actual computer "business'" and don't rely on it to make a living. They know what they are doing and have clients but don't have storefronts or file taxes as a business. It is hard to really say how much you will make and what would be good advertising for your area because we don't really know where you are. The biggest issue with opening a storefront computer business with no customer base at all. If you honestly think you are going to even make a profit in the first month you are most likely in for a rude awakening. Most small businesses don't post profits till around the 6 month or a year mark. If ever. and with no customer base beginning you are shooting yourself in the foot by opening a storefront shop. You have to factor in rent, bills, insurance, and other costs such as inventory as well.
Another thing you need to factor in is your potential competition. Places such as best buy, geek squad, and other potential computer repair shops who are already established in your area. People are creatures of habit and if someone has already fixed their computer once and it worked how they want they will most likely go back to them. Average users are scared of computers and feel they have no clue how they work and don't trust strangers with them either because they feel they are too complex and not just anyone can work on them (
You also have to list what services you plan to offer and get a list of services offered by your competition and see if you can compete price wise with them and what services they don't offer that you can.
As with any business you need to get started somewhat before you even think of opening up a storefront because of all the expenses you will come into and not having enough capital in the beginning to be able to afford the start up costs and potential losses is what makes many small business' fail within the first year. People think that if they open up a business that customers will just come in and make purchases but it doesn't always work that way and with the overhead of a storefront bills pile up quickly.
I'm not saying it cant be done but a lot of research and funding has to be done before you jump into it. With any business you will get out of it what you put into it time wise. The more you can compete with other companies plays a HUGE roll as well because at the end of the day if someone offers the same thing for cheaper it is REALLY hard to compete especially in this economy.