If you operate as a sole proprietorship, you only need to file a Schedule C with your federal tax return. You need records for gross receipts, mileage, insurance(if you maintain an e & o policy or liability insurance for a studio location or have equipment insurance), rent (for a studio location, equipment etc), If you have a studio, you will need utility bills. Also, receipts for long distance telephone calls related to you photography business, business cards, postage, advertising, payments to assistants, printing, etc.
To better establish your photography as a business, open a business checking account. In the event that you have two or three years of operating at a loss, this will help keep the IRS from claiming you have a hobby loss as opposed to a business loss.
Cameras, lighting, backgrounds, stands, computers (will be treated as listed equipment and prorated between business and personal use), printers etc can be depreciated straight line or you can take a section 179 deduction which allows you to take a form of accellerated depreciation, but may also require a depreciation recovery in the event the equipment is disposed of.
If you incorporate, you will need to keep up with you organization costs which will be amortized over 5 years.
You may want to get a program like quick books to keep up with your expenditures. You can even direct certain categories of expenses to particular lines of your tax return.
Check with you state sales and use tax office for instructions on collecting and remitting sales taxes. The laws vary from state to state, and it may be possible that you collect taxes on prints but not on sitting fees.
If you have all your information together, you shouldn't have to spend hours with your cpa. Most expect you to have your ducks in a row when you come in.
Good luck.