Most of you guys posting are acting like you are that living room/garage/basement "store". If you sell coral here or there out of your tank to get a new piece of equipment or a cherry coral you have been eyeing up at your LFS that is cool and makes the hobby fun. Sadly I know a few guys who have chosen to buy a business license just to get whole sale accounts and sell straight out of their living room, garage, or basement. Yes they have little overhead so they can keep prices lower but if they aren't reporting sales, paying sales tax to the state, paying for insurance, paying for a separate rent/mortgage how could a LFS compete. They literally order from wholesale, chop it up and put a tag on it. If his illegal business puts down my local brick and mortar LFS I'm not going to be happy. That way of "business" should come with a made in China sticker, they take shortcuts in order to make a quick buck and jeopardize true American business. I can honestly say I have not purchased from that kind of "business" or even online websites because it is hurting the local stores who know your tank and do what they can to help you and keep your business.
- end rant
After reading your post here are my thoughts. If they have a business license then they are a legitimate business. At that point they have the right to buy wholesale and to write off business expenses. As to insurance if they fail to insure themselves that is there choice but a really stupid one, they would be risking there business as well as there home if something were to happen and they were found liable. Still any business could do that legally. If they fail to report there taxes properly, that is illegal and a separate matter. It is up to the IRS audit them, just like anyone else. If it bothers you so much you should be able to get information about there business from public records including there tax returns. After that if you were positive they were not reporting properly you could try and blow the whistle on them. I would think that if the LFS thought a specific garage business or businesses were seriously hurting them they would have already done this. Sales Tax is probably the easiest one to look at as you do not get to deduct anything from sales tax reporting. Annual taxes are much harder to look at and know if they are fudging there numbers.