If you are just starting out in the business of photography, do yourself a big favor right from the get go. Find software like Quickbooks or Quicken and keep track of all your expenses and income from Day 1. Set up a company bank account that is separate from your personal account. Figure out what type of business you will be (LLC, Sole Proprietor, Partnership, etc), and how to properly pay yourself through your new company. That way you can easily follow every aspect of your business as you grow. You will be able to look at your marketing investments and see which ones are working and which aren’t. You will be able to compare your income year to year or even track which months are consistently your slowest (and then you’ll know when to do an extra marketing push). Set everything up correctly from the beginning and your life will be easier down the road (and at tax time).