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.