It is not all good:

An important deduction for small business owners that would disappear under the flat tax: the deduction for one-half of self-employment tax paid. All small business owners, including those who own the smallest of home-based businesses, are currently entitled to this deduction because it helps to offset the self-employment tax paid on their profits. Currently, employers and employees each pay half of the 15.3 percent that is taken by the feds for Social Security and Medicare taxes. Self-employed individuals have to pay the full amount, hence the deduction for one-half of self-employment taxes paid.