H.E.L.P Cheapest place to hire a good mobile app developer

[abdulatifx]

I am trying to get the app idea from concept to product. As most of us know, that we can produce most of our ideas ourselves ,though it's hard to drive a car and preform all the operation functions àt the same time. So here I am.
I need help locating a freelance app developer and graphic designer for this app idea I've been sitting on. The idea isn't brand new. But my niche well be.
Things the app developer would need to be able to compile:
The app will need to link in/up to a server/network-
It will deal to gps proximity for users-
Users will have various authority levels-
Users will need to be able to link to an central payment medium.

That's the gust of it, sure there are more aspects to it ,but that's the largest function of the app.
So it's not some simple 1 hour app design, it may have multiple programs involved with it.
I'm not trying to solicit a developer from BBHF (maybe the graphics developer), but I'm trying to determine where's the best rated freelance resource I could use.

Fyi: I'm familiar with elance, freelance, etc: though by not having dealt with them ,not sure whom to try out.

THANK TO ALL
Your bbhf member:
Abdulatifx