Just two cents worth here ... okay maybe a dime's worth ...
First, you should have a general idea of how long a drafting job should take so paying by the hour is not always a bad idea. If you are hiring someone for the first time, do it by project and ask them after it's all said and done how long it took and tell them why. You have to establish a rapport or you'll never get the quality you want. All a freelancer has going for them is their work and their reputation. You can see what their work is like ... and after working once with them you can see if they take pride in their work or if they are just "trying to rack up hours." Those are the ones that will not make it independently.
Second, one of your best resources for drafters is people who have left your firm in good standing or, if you outsourced it, their firm in good standing. If you know the drafter's work, you know what to expect. If you can't get that info from the firm, if the person is freelancing it, you can do a search from the name on the plans. You can also ask at your local blueprint shop because independent contractors will utilize them from time to time. Leave your business card there. When you are getting permits etc. leave your card or just talk up your needs. Again ... it's all about rapport and networking.
Third, anyone worth their salt is going to have good references and letters of recommendation. Not just from former employers but also from clients and officials they've had to work with. And they should be able to show you examples so you can see if their style is just lines or if they include everything you ever wanted the guys in the field to know. Most will have examples of both, as some employers do and some don't want that information on there. The good ones I know have been out in the field so they have an understanding of what is going on there. Flexibility is what you're looking for.
In the end, hiring a reputable draftsperson will save you money. If you pay per project or by the hour, you still don't have to pay benefits or for down time. You can upload to the independent contractor's web site or use FedEx and charge the FedEx back to your client and it will still come out less overall.
And while outsourcing to other countries is fine (although I personally am against it) there are lots of people in your country who will do the job for the same or slightly more money. When you've just been laid off, you don't want to do it for less but when you've been laid off for a while or are just establishing yourself independently, you'll take work at lower rates.
Once that person is established, I guarantee there will always be consideration for a good client who was with them at the beginning. The first job you get at $15/hour should be just as good as the most recent job at $50/hour. You want someone who is proud of their work, not of how much money they can squeeze out of you.
Bottom line ... if the draftsperson is good and honest and you are specific as to what you want, you will wonder why you didn't hire an independent contractor before. Try it out before you need to actually utilize it (like in a non-critical overflow situation). The hardest part, IMO, is the lack of "hovering" you'll have to do
