Not necessarily for pets - food, eggs, skin (ostrich skin boots are quite popular and the ones I’ve seen are quite expensive) and feathers.
Unfortunately, the bottom seems to have dropped out of the ostrich/emu market, and several ostrich and emu ranchers have lost lots of money on the birds (one chick can run about $5,000, and up to $25,000+ for a breeding adult). In some cases, they will just open the gates and let the birds loose: I’ve received reports from confused drivers in eastern Orange County and Lake County who swear they are “…not drunk but I just saw an ostrich running down the road!” [Advice - call animal control.]
It takes a big yard, and one that is well-fenced, not only to keep the animal in, but dogs and curious and/or nefarious humans out. One good kick, however, and I’m sure they wouldn’t be back too soon.
Then again, I knew people who had llamas in their yard.
As far as the OP, there are several species of tropical and temperate penguins - the Galapagos, as mentioned, the Black-footed (or Jackass) Penguins [South Africa], as well as a few species off the coast of Peru, not to mention the Fairy Penguins (or Litle Blue Penguins, as I’ve also seen) [New Zealand?]. Probably a few more, but most of my library is dedicated to Florida and Northa American birds, some South American passerines, and general field guide of other countries: general info, but not much on penguin locations.
Problems in keeping a penguin -
[li] Special feed (how much herring, smelt and krill can you stockpile?][/li][li] Medical care - got a vet that deals in exotic birds on call?[/li][li] Odor (not pretty)[/li][li] Permits (required for keeping most protected animals in captivity, not to mention annual and surprise inspections of your facilities.[/li][li] Odor (really not pretty)[/li][li] Waste products - very liquid, and house-training is virtually impossible.[/li][li] You can get a significant other, how about your penguin? Ready to double the size of the enclosure, provide nesting materials or dig a burrow (for the Galapagos)?[/li][li] Don’t know where you live, but are you going to stay on Northern Hemisphere or Southern Hemisphere season? (Several zoos switch the amount of artificial light for their penguin and koala exhibits, simulating longer S.H. summer daylight while we have our N.H. winter shorter days.)[/li][li] Temperment - watching two Rockhoppers (known for their bad attitudes) fight was not pretty. Seeing the aftermath was worse. I imagine getting bitten is not fun, after seeing the damage they inflicted on each other.[/li][li] Noise - they vocalize some of the strangest calls. [On tour at SeaWorld one day, my companion remarked that they sounded like several of the senile patients he transports daily (he’s an ambulance driver) - the barking, moaning and chirring was about the oddest sounds I’d ever heard.[/li][li] Odor (no more need be said…)[/li]
All in all, a nice thought, but stick with something more traditional. Mr. Popper just put his in the refrigerator (“Mr. Popper’s Penguin” - can’t remember the author), but there’s a lot more to it. And of course, my main book on caring for exotic birds is missing.