SQL Server / Oracle DBA Consulting – Charge Rates? Demand?

I’m a senior DBA at a large Boston company who’s looking to get into consulting. Any advice on these questions would be greatly appreciated…

What is a typical charge rate range for DBA / database programmer?

What’s the best way to get started and get your foot in the door(s)?

For the full time consultants out there, how many hours per week and weeks per year are you usually able to bill for?

advice…. advice… advice… Please, the more the better!

Thanks!