Before the travel industry contracted 50 percent during the economic downturn, the industry average gross profit margin was 22 percent. That means many agencies had an even lower profit margin. So that so-called 80-20 plan, or partnerships is marketing baloney. I always have a good laugh when I see that agency's advertisements. Opening a new hospital for an agency means that they will be making lots more money placing other travelers there while you get nothing for helping them.
I'm all for independent contracting, and I have been doing it exclusively for the last 8 years. You get to keep the entire profit margin for yourself, increasing your pay tremendously. However, that is not for everyone, and there is another way to do what that agency is suggesting. Basically, it is either going to a hospital you have worked before and they want you back, or cold calling the manager and inquiring about the possibility of a travel assignment (which works better if you happen to know they are already looking for a traveler) - that usually turns into an interview on the spot. Now you have a lot of leverage. If you have a favorite agency that already treats you well, they often can obtain a contract with that hospital based on the manager wanting you, and should reward you by paying you even better than previously.
Alternatively, once you have that "in", call HR and ask them what agencies they have existing contracts with. Then you can negotiate with those agencies and play them off against each other from a position of strength. After all, you are handing them approximately $5,000 gross profit on a platter (what agencies typically make on a 13 week assignment).
By the way, that is exactly the scenario it takes to do the contract independently. Once they want you, you have leverage with HR to do your own contract. You need to have a contract written, get insurance, and a few other ducks in a row (basically presenting yourself as any other agency), but it is not especially difficult. Just requires a certain inclination, and some set up.