> Expect to get paid about half of what you would for contracting work you source yourself.

Being in a position that hires said contractors, I have to say this is false. Rates are competitive; we're not the one's setting them, the market is. Recruiter's commission may play a factor where it's involved, but it certainly doesn't halve the rate.

I'd also say "good luck" to acquiring contracts in your area of expertise directly from the companies that are buying them. They're looking for complete packages and the effort involved in acquiring and maintaing those relationships is quite often beyond the abilities of a single person.