Basically, RH Proxy means just the Proxy server has internet access and all the rest go through that.
RH Satellite means completely off the net (although you need some method to update it of course).
Spacewalk is basically the free / upstream version of Satellite.
Theoretically you could custom build something using https://code.google.com/p/iredmail/w...Yum_Repository
HOWEVER, as JohnVV said (and please don't take this the wrong way), if you're asking this sort of qn, you REALLY should come up with the money for one of the RH solns, at least for 1 year, whilst you get yourself up to speed on the technology.
This is not a trivial exercise, especially as you're implying this is for Prod servers, where you cannot afford to mess up.