I don't deal with camera equipment, but I do deal with automotive stuff as a retailer...generally you need to get setup with the manufactuer or a distributor to get the product. most of the time you'll have minimum purchase levels that you need to meet, and an ongoing amount of sales to maintain your status as a 'reseller' or 'retailer' (something like a $20-50k+ buy in per manufacturer and likely something like $20k in yearly sales would be a guess at the figures you'd be looking at, though the camera equipment market is likely different than what I'm used to)...
your best bet is to contact the manufacturers directly and talk to them about your plans, and inquire about how they are setup with retailers, if you can get into industry conventions, that is usually a good place to make face to face contacts. Ideally you'll already have a business setup (i.e. tax ID, DBA, business address, etc) possibly even a physical storefront (and web too), sometimes manufacturers won't take you seriously and may not even respond to you unless you have some kind of established buisiness. it kindof depends on what amount of funding and income you already have as to how you progress, if you're just getting started without alot of startup capital at your expense, you may want to start a small business that will allow for expansion into a retailer area (say start a studio, or printing service first, get established and profitable, which likely will take a while, then build into the retail sales aspect), which will take ALOT of planning and foresight. start by researching and writing a business plan, what you want to accomplish, how plan to get there, goals, etc...
photo retail is likely a very hard field to get into and maintain profitability in, you'll be competing with huge operations like
BHphoto and
adorama, Ritz, best buy, and many others...It'll be VERY hard but not impossible, and profit from the business may not be seen for years, even if you're doing it right. I don't want to discourage you if this is really something you're looking at, but keep your short term expectations realistic and keep building what you want it to be....if you're not already well versed in business, you'd probably benefit greatly from taking some courses in business management, marketing, accounting, etc...there's far more BUSINESS than PHOTOGRAPHY in the photography business...if that makes sense.