Originally posted by griffith jones:
Been down this road myself; was incorporated as a "S" Corp in California for 9 years ...
Lots of paperwork and 2 sets of tax returns for an S Corp; C Corp is considerably more complicated, and probably not worth it for a small consultancy. LLC is simplest of all, and has most of the benefits of an S Corp, and you don't need a separate return for it, as far as I know.
Check your local regulations, but there is usually no license needed, beyond what you need to set up any small business, i.e., filing for a business name, fed tax ID, etc.
In California, there are internet sites that will set up an LLC or S Corp for around $400, including filing fees; you pay $800/yearly minimum to the state in tax. For a S corp figure $1000/yearly for a tax accountant. You'll probably want a payroll service too, such as Paychex or EDP. Another $400-600 yearly there.
Be advised that many major businesses work only with a select few vendors from a preferred list, you will have dificulty getting on this list. If you ever do get on the list, it can be a license to print money -- favored vendors are in a position to bring in their own people as a significant markup.
You'll definitely need business insurance, i.e. "Errors and Ommisions", so a talk with an insurance broker will probably be in your future.