I'll warn you though that the type of arrangement you suggest does exist, it's called: 'a consulting house' as opposed to: 'a software bouse' and it is the worst kind of scam.
First off, your 'market rate' ...that you can forget. The Firm sees to its own needs and those needs are fat salaries and bonuses to (non technical I might add) management. You'll get a salary and a fancier title than 'contractor' something like... Say... 'consultant' yes! Consultant! That's gonna bump up the hourly rate... But not YOUR hourly rate of course, that of the Firm my friend.
I guess my bitterness in this regard is quite obvious but here in South Africa, this type of thing is utterly rife. You have a few managers who have swept in over time on the winds of apathy and who for some I fathomable reason have good, big contracts and a slew of underpaid 'consultants' who run around doing their bidding.
You seem to believe that this relationship will play out the other way round where you are earning that 'market rate' and for a small percentage of that you'll have in your employ not only someone who'll ensure you're always employed but who is also a personal assistant that runs your admin?
That's called: 'a boss.'
Please correct me if I'm wrong here but it seems you have the world (as I know it) bass ackwards and programmers are not Hollywood stars, not where I come from.