First I'll paraphrase the old farmer joke:

Reporter to Game store owner: Now that you've won the lottery what will you do with all the money?

Game Store Owner: Well, I guess I keep running the store 'till it's gone.

Seriously

Don't underestimate the amount of money you will need. Advice often given to small business startups is to have enough money to stay in business for a year without any money coming in. This sounds unrealistic but you'll be setting yourself up for failure if you try to do this on the cheap.

Don't underestimate the amount of time spent doing Back Office functions like bookkeeping and inventory (God help you if you have a real employee) You'll do plenty of these things and probably still have to hire an accountant to do the taxes. (Depends on you knowledge and how you structure your business.)

Don't start acting like a big time business owner. Having friends call the "800" number for personal calls and giving money to belong to business organizations is a quick way to those months when you have no idea how to pay the "net 30" invoice that is now hitting 60 days.

When it comes to credit terms -- don't use it right away. Try to have enough money that you don't need to use net 30. It's too easy to think that stuff will sell when it really won't. At the regular profit margins you'll need to sell half of the order within the 30 days. That might happen but what if it doesn't? Too easy to make a bad decision because you think something is cool and will sell. When you have to pay out the money up front you tend to make more thought out decisions.

Don't turn it into a partnership. Too many people have no business sense but once they are "owners" they want to have as much say as the next guy. (They also want to act like big business owners). If you don't have the money and must get others to invest, try to get it from people who have no gaming interest. You will all have the tendency to think your favorite area will be a big seller with just the right amount of support and, of course, inventory. So you end up with lots of specific stuff that the average gamer could care less about.

Carry the card games, carry GW, carry the stuff that sells and use it to subsidize the other things that don't sell so well but that you still want to carry.

Do mail order and Internet as soon as possible. It helps pay for the rest of the business.

I don't mean to sound so negative but I've been there and I've learned some lessons. Lucky for me I could afford the loss. Which brings up another point - You'll be much more committed to the success if you have no other option but making the business succeed. I was able to swallow the cost and get out so I probably wasn't as committed as I should have been. (Plus the frustration with my partners was very high.)

Someone pointed out some time ago when this idea was being kicked around in this group - Look at phone books from 10 years ago - How many of the game/hobby stores listed there are still in business? Do the same for 5 years ago. It's a sobering realization.

Really, good luck. It can be done but I don't think it's as easy as we lead ourselves to believe.