The author having found a great guy after 1 week for only $20 sounds to me like he got lucky. And that's not considering the side tasks he gave to the developer just to test him. And the other guy he hired before but didn't like. Summing all that, I'd assume that on average it would take at least two months just looking for someone good and finally get started working on a real project.
Does anyone else got similar good experiences like the author and could confirm that it's actually not that hard? Or did the author just get lucky?
Your main advantage will be to take the requirement and break it down into its lowest parts and then hand off those parts to an outsourced developer and if he/she does not deliver exactly to your spec, then end the relationship. Period.
There is a fine line between clarifying and micromanaging though.
Initially I start by posting the job, then filtering in stages before asking them (and paying them) to complete a small 1 to 2 hour coding project. The coding exercise can be done many different ways but the purpose is to evaluate problem solving, code quality, knowledge of libraries, code structure, etc. It's amazing how much insight you can gain with something like that.
More importantly, having them work on something real helps me further evaluate communication, responsiveness, and other attributes I look for in a good dev.
The rewards of finding the right developer far outweight the upfront cost of looking for one in my opinion, but it depends how long you are planning to be in business for.