To me, this just sounds like a referral business. Depending how you lay your contract and Scope of Work out would determine if I would recommend this if you like working. I understand it's everyone's dream to just let other people work for you, making you money. This model would be great if you had multiple deals going on at a time, with multiple "contractors". Screw it, call them employees!
You are right that you need to worry about quality as well; remember the old adage, "if you want it done right, do it yourself". If you decide you can trust others to do your work, you need to remember a few things:
- You need to pay for QUALITY work. This is not always true, but it will keep the good workers around. My previous employer lost me because he did not pay me enough, but I saw what we were making. I also had to educate and help other contractors who were paid much better then me, doing things that I always did simply. You need to pay enough that they want to do well, but not so little that anyone would just leave for an extra $1 or $2 per hour
- Supervision needs. Do you need to watch the contractor, or do they have enough of a track record you can leave them to do their own thing? Most people prefer to work on their own, without being micro-managed; you need to trust the people you hire to do the work. At the same time, if the contractor has never done this specific type of work before, you may need to mentor them, and you can go through the quality standards as well.
- Layout in your Scope of Work the estimated time of completion, and PAD IT. Mistakes will happen, no matter if you do it yourself or hire someone else to. Depending on your project, you'll sometimes run into times where skipping one section resulted in a domino effect, killing everything else. You don't want that. In the Scope of Work for your contractor, include the times that they have to complete the project, as well as the standards you expect them to adhere to. You must be specific! If you aren't supervising, make sure they have all the instructions they need, and write them so a 12 year old could follow them.
- Taxes/Deductions. Depending on your contract depends on if they require a paycheque (i.e. holding back taxes, paying Worker's Compensation Benefits, etc), or just a simple invoice-cheque solution, you should check with a lawyer as to what would be required on your part as the "manager" of the project
Edit about Share Ratio
There is nothing wrong with sharing the profits, and your contractors will want a bigger piece of the pie if they're doing the work. If you want to keep more of the money, then you need to only give them the easy, remedial stuff that you don't want to do. This is the only way to negotiate a larger amount for yourself. If your contractor knows they're doing more work, they'll start asking for more, and you can pick a good share ratio. Having said that, I had started off my first two contractors at minimum wage +$5/hr, as they were just starting out and I was supervising them and teaching along the way. This was great for them. I am sure that when you get people who have been in the industry a while though, you'll have to up the price. I don't believe you can give a percentage, but that's just my experience in my town.