Before you can figure out if your expense are reasonable, you have to know how much money your household is bringing it. Start by listing all income from your job and that of your spouse. Include any side jobs or hobbies that also bring in income. If you have rental income, list that as part of the budget as well. Finally, for the more advanced financial families, add up any investment income that is not in a retirement account. List all of the income in a single column on a spread sheet, or give it an entire sheet all its own.