Incorporate? Skip It
Many "starting a business" guides will encourage you to incorporate, citing the legal protections that such a move offers. Their assertions are true, but unless your new venture is selling herbal Viagra online, your risk of facing a serious legal headache while your business is in its infancy is minimal. It's far cheaper, easier, and faster to operate as a sole proprietorship, especially in dealing with finances and taxes. If things grow complicated, you can always incorporate later.
The Simple Business Bank Account
You can open a second bank account if you'd like, but if you're a proprietorship and have a DBA, you can use your personal bank account for business and not have to worry about multiple accounts. Your bank will even print your DBA on personal checks, making them suitable for business use.
If you really need a second account, ask your current bank if it has any special deals for small businesses. Many banks, for example, offer free business checking if you maintain a certain minimum balance.
Set Up a Switchboard
If you're expecting a lot of incoming phone calls, an answering service might be worth the investment: You'll seem more professional to customers, and you won't be roused from bed at the crack of dawn by callers who don't understand what time zones are.
You can have a live answering service (similar to the one your doctor uses) for $20 a month--or less, if you have minimal incoming calls. Another option is to do it virtually: For about $10 a month, you can get an 800-number-based system such as RingCentral that answers calls with an automated greeting, routing calls to you (or other employees or contractors) or to voice mail depending on button presses.
If phone calls aren't a big deal, consider a second landline or a dedicated cell phone that you can use for business: Adding a line to either is easy, and with a cell phone you can even share minutes under a family plan.
For a Little More: Get a Virtual Office
The world doesn't need to know you're working in your basement, so many business owners turn to a P.O. box for the official address of their company. A bare P.O. box, however, doesn't seem all that professional, and you can't receive UPS or FedEx shipments there.
Another option is a virtual mailbox service, such as that of Regus. With a virtual mailbox, you get a physical mailing address and someone who will sign for packages from other carriers. The catch is that people sending you mail still have to put a PMB code on the envelope, though it's less conspicuous than with a regular post office box. You pick up the mail once a week, or the service forwards it to you at cost. The plans cost $100 to $150 per month.
You can step up from there to a more serious arrangement: A virtual office setup gets you not just mail service but a live receptionist who answers the phone however you like, plus access to a physical space with offices, conference rooms, and even videoconferencing facilities. Fees can range from $250 to $325 a month.
These costs are admittedly beyond our $100 budget, so consider whether you really need them before signing a contract. With so much business conducted online and via phone, you may never deal with visitors at all.
For a Little More: Offload Fulfillment and Shipping
Selling physical goods online often means long hours spent in your garage packing up orders to ship to buyers, and then standing in long lines at the post office to mail it all off. Another option exists, thanks to the wonders of e-fulfillment: You pay someone else to do all the inventory handling and order shipping for you. Fees can be pricey unless you have the volume to mandate it: Efulfillment Service costs $70 a month flat, along with $1.85 per order processed and $0.25 per cubic foot per month for inventory stored, plus actual shipping fees.
Alternatively, you could hire a student or other temporary help to do the work for you a few days a week, but you'll still have to find somewhere else to park your car.
By now your business should be up and running--but that, alas, was the easy part. Now get out there and publish, promote, and sell, sell, sell. And remember that even if, in the worst case, your business fails, "CEO" always looks good on your resume!