Yeah, definately. Start off with two of good quality (I got two very very nice Rams for $15 together here in Michigan), and treat them right with some plants and do alot of research, and you can easily sell the fry back to LFS. My female died, or I'm sure I'd be doing the same. One LFS (A Something Fishy) offered me $2 for each fry, up to 100. So, there's definate money, ever more with butterfly rams, but they're hard to get ahold of.
Angels are beautiful, almost as nice as German Blue Rams in my opinion. The wild caught Altums are slightly trickier to breed, and I've seen some at a breeders that were 14.5'' tall, but Scalares are abit smaller, and easier to breed, and will still bring in money if you want them too. I think 80-90% Coverage Kois are about $50 a pair, so they're an option if you get further into it and get the hang of the genetics. Plus on here there's even an Angel Fish & Discus section. there's also entire forums dedicated to Angel fish, where alot of breeding gurus discus Angelfish.
If you don't want to do just a couple fish in this tank, the foot print on 30ls are good for Tanganyikan Shell-Dwellers. Around here, there's pretty neutral demand for them. There's no big hype, but people will usually take them off your hands at swap meets and definately online. Cichlid-Forums, where I'm pretty sure you're a member, usually has some for sale in their trade/sell/buy forum, and they get snatched up pretty quickly, so there's definately a market. I myself are looking into it for a spare 20long that I have sitting around.
I don't really have experience with Kribs, but they look nice. ^^
And another suggestion if you think you can handle the slighty-above-average demands of the fish are Discus. It may be more expensive to get started, but they're more than a joy to breed I hear, and again, there's numerous forums and sites with loads of information about them. The various strains and bloodlines will make your head spin, and I think that's part of the fun, personally.