Good luck with your venture. I'd suggest you contact New Hampshire's small business development center. They will have a lot of resources for getting started, options for funding, etc. Their website is http://www.nhsbdc.org/
RE: market trends, I'd suggest you focus on researching the local market--for example, how many homebrewers in the area your store would serve, how frequently they brew...which you might be able to estimate based on information from local clubs and competitions. National sizes and trends are only relevant to what you are doing if you plan to launch a webstore, which might not be a bad idea.
I'm not in the LHBS business but it seems that the critical success factor is getting regular turnover on your ingredients to keep them fresh--in addition to good service and competitive prices, which I would consider a ticket to play. There is probably some threshold size of the business that you need to exceed in order to keep your turnover good.
Also, consider striking up relationships w/ local brewpubs and possibly supplying them. There may be some situations with things like specialty grains where it could make sense for a brewpub to buy from you rather than a grain supplier. I also know my LHBS sources grain for my local brewpub. This could provide a nice source of income to finance the store through the early stages of growing your homebrewing customer base.