You absolutely have to..uh... register it.Our gov t wants it s fair share in taxes.You need to contact an accountant and tell them about your business that you d like to have. They ll help you decide if it should be filed (what you re calling registered) as a limited liability company, an S corp. , a self proprietorship or a limited Partnership.You re accountant will help you decide which one of those to file under inorder to make sure you will pay the least amount in taxes based on what state you live in.Now, as far as getting the big brands, simply contact their corporate office - easy to find on the web - and tell them you want to be a distributor of their products. They ll make you fill out all sorts of credit applications and give references because they are not idiots who just give away thousands of dollars of merchandise to strangers because they have promised to try really really hard to sell all of it for them.
clothing store is one of the worst kind of businesses to open right now - you better write a business plan for whatever type of business you want to open and prove it can make money - lot s of research involved and lots of money and/or credit needed too