Starting from the ground up with no clients and trying to build a client base on this model would be difficult. If you can't show results, I'm not going to give you 10% (or any other percentage), mostly because so far I've been DIYing it and doing decent. But if I already had a "relationship" with a recruiter, maybe one who's actually good at technical placement and they found something good for me along with offering to be a long term career guide / mentor / agent, I'd be interested in listening to them much more than if someone just calls me out of the blue. And if the pay was more than I get now, even with the 10% cut taken out, and involved interesting projects, that would get my attention.
I think the long term career guide and mentoring part would have to be a big part of it. I know my skills but I don't necessarily know who out there wants them, maybe there's people out there who need my skills but also don't know it. The agent comes into play here and matches up two people who don't know they really need each other in order to make great things. This takes a lot of work on the part of the agent.
If you have this business model, managing 10 to 20 developers and taking 10% cut of salary, that's enough to make a nice living on and you'd have time to be personal with all of them.