Tips for a realistic estimate
Get real quotes for your largest costs rather than guessing, and remember costs that are easy to forget, such as permits, insurance deposits, payment processing fees and your own living expenses while the business ramps up.
A contingency buffer covers surprises. Fifteen to twenty percent is a common starting point; use more if your plans depend on construction, imported inventory or hiring.
Once you know your numbers, a business plan helps you explain them to lenders and investors.