I vote for the talk to an accountant approach -- let the accountant advise you on the business accounting and tax record requirements.

File a DBA (doing business as) name if you want with your county clerk's office. It costs $10.00 for 5 years here (generally cheap).

And like said above, use a generic non-porn name to open your business bank account.

For discussion purposes and not legal or accounting advice:

To trademark a name costs about $500 (DIY) - $5,000. Succeeding in trademarking a name can vary a lot and get costly when there is a conflict name dispute. Consider the current value of what you are trademarking and its likelihood for being worth the cost. If the trademark is speculative on your efforts trademarking is not an amortized expense but site development costs can be current expenses or amortized.

Try to always use a business bank account debit card for business related expenses -- that creates a record of the seller and the amounts spent -- you need to keep the original receipts for detail if you are ever audited for taxes.

If you work out of your home: To fully utilize the home office deductions you need to use a dedicated room for the business. Office furniture and supplies are deductible (accelerated or amortized). Hosting costs, domain fees and business ISP service are deductible. Business telephones and service are deductible. Legal fees, accounting fees, computers used for the business are deductible.

You need to compute your business income on a schedule C basis and pay estimated income and SE taxes (if in the USA) quarterly or pay a penalty at the end of the year -- consult with an accountant.

Quicken and Peachtree accounting are good accounting programs for small businesses -- ask your accountant for what he recommends.