Clothing Boutiques In Los Angeles

What are the legal- and/or paper-work required for starting an online clothes boutique in Los Angeles?
I want to start a “ModCloth”-esque retailer and I was just wondering what needs to be done besides the business plan. Also, how much will it approximately cost, or cost on average? Thank you to all who answer.
a virtual store wouldn’t require an actually building, you could just send the clothing off to people who want to buy your clothing, I don’t think you would have to do any paper work except that your planning on running a business through your home and to pay taxes on what you sell, I believe I am not sure.
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