General rule of thumb is to put aside 20 - 25% of every $ you make for estimated taxes ... once you know what your profit margin is going to be the % can be adjusted. Using a good bookkeeping system will help you determine your profit margin.
Also paying in 100 % ( or 110% ) of last year's tax liability will help you avoid an underpayment penalty. Discuss this with whoever is going to help you ... get all the education you can for the buck you are paying.
