Ringnecks are fairly easy to raise.  Smaller pens are possible if you keep one rooster per pen with multiple hens.  Warning, the suckers fly at an early age, like a week or so.  As far as feed, they really don't eat much compared to turkeys or CX.  Feed is more expensive (higher protein), but price per finished bird is reasonable at about $10 per bird at 8 weeks or older here.  You should check into getting a gamebird license if you will sell them.  
In Washington it is $72 for the GB license, plus an inspection, testing on a percentage of birds, and some basic record keeping on who you sell birds to.  If you were to sell 100-200 birds per year, you would likely cover your pen costs the first year and break even, and then from there on out you would be looking at a minimal profit unless you go whole hog.
We are only raising enough birds to cover feed costs and give us enough birds to do some training.  If you set your initial goal to break even and you actually cover feed costs, it allows you to learn the "species" without a huge outlay.  
I started with 10 ringnecks.  Lost 2 early on, just died.  Had one escape, now I have 7 left.  If I didn't sell eggs I would have 150 chicks + eggs in the incubator, and it would be quite easy to raise 200+ birds from these 5 hens.  Depending on the scale you wish to achieve, this will give you an idea on minimal productivity.
I would suggest bringing in fresh blood, males and females, on a yearly basis.