In the US it *IS* required to have a business license from your city. A Simple DBA (Doing Business As) will suffice for many people starting out, but it *IS* required by law if you have a business (also necessary if you try to open a merchant account at your bank). You may not need an LLC Corporation license, this depends on how much risk you want to assume etc. However, personally, if you're starting a business, I suggest getting incorporated so that you are personally not sued by someone should something come up (you'd still be responsible for gross negligence claims etc).
One thing that I caution you on however is that you had mentioned that you worked for a hosting company but quit because your other job was taking too much time. Be aware that starting your own hosting business is not a walk in the park and most clients are accustomed to 24x7 (or near 24x7) support. Just something to be aware of in the back of your mind.
You should also make a good business plan and stick with it. Starting a business should never be done on a nickle budget. Spending the few hundred dollars to protect your liability is well worth the money. Putting $20k into opening costs is usually not necessary with an online business, but having $1k-$2k for immediate advertising, graphic design, corporation papers, initial few months operating expense SHOULD be in the pocket. If you're going full time into hosting, then having a loan for $15k would be ideal as if you pay yourself $3k/month that will at least help you float for the first 4 months while you build a client base.
You *CAN* get into the web hosting business, or any online sales business on a shoe string budget, but it will take you quite some time to be profitable if you have no money to start.
The old mantra still holds true today - "You have to spend money to make money"