i just can't see them being worth it, the most you can get out of a single hatching is 2 birds, and to feed the average family of four you would need at least 2-4 squabs, it takes 18 days for an egg to hatch and then probly at least a month to get the babies up to weight, and pigeon food is way more expensive than other kinds of bird. So it'll take 2 months (minimum, probly more) for the parents to raise the babies and then start on another clutch, plus you'll probly end up saving some of the babies as breeders, you'd need alot of well managed pairs to make this work. I'm sure they did use pigeons in the great depression, but back then alot more people had pigeons lying around and feed was comparatively much cheaper. Look into coturnix quail, they lay every day, the hens start laying at 6-8 weeks and the males are at a butcherable weight at 6 weeks usually. All you need to get started is 3 or 4 hens and 1 male, that will give you 40 fertile eggs in ten days, put them in a cheap incubator and they hatch, they'll hatch no matter what, literaly.