I've know quite a few inspectors in your scenario. In fact a few of my closest friends that are local inspectors have 2-3 guys working for them each. Times are busy right now for them. Here's my 2 cents, I'm sure the other guys here can give more information (and better).
The reason an inspector would work for you is easy. They are just starting out, or maybe inspected a long time ago and just getting back into the swing of things, or even have their own company, but can't drum up the business. There's a lot of reasons an inspector becomes successful but the point is, right now you are, and many other inspectors in your area may not be. You're doing things right. If the other guys can't make it on their own, getting jobs from you works nicely.
In general I've seen the hired inspectors get a percentage of each job. At this point, you're not gaining a partner so you're not sharing a percentage of overall sales, you're hiring an employee so you're just paying them. I just called an inspector (Mike Verlingo, he's posted on here a few times) that I know does this. He says he gives the inspectors working for him 70% of the inspection price. Two of the guys that work for him actually work for 2 other inspectors as well. They don't have to worry about advertising costs or any marketing as they just get the overflow from the 3 main inspectors (3 different companies).
Also, Mike said that the inspectors are able to get E&O insurance under his company name at a greatly reduced cost as an additional employee, but not all E&O insurance companies will do multiple inspector policies. He's going to forward me the info on who does his as his extra inspectors are only $300-$400 a year each.
There's a few very important things that you have to be careful of when hiring inspectors to work for you. One has been an issue with many guys I know. You have to make sure that the inspector working for you doesn't run off with the agents you've built a reputation with. It's important for you to keep in close contact with the agents. Whether you purchase Home Inspector Pro or require the inspector to, one of the benefits is that the company name (YOURS) is locked into the program. So every report has that information locked. You will want to make sure the inspector keeps your phone number on all the reports, your address, etc.
Hopefully this has been helpful. Mike Verlingo said he'd come on later and post, he's on a job site right now when I called him.