Well Colby, I guess I should maybe share my orchid experiences - for a few years after getting out of the aquarium industry I didn't run any tanks but instead raised and sold orchids (
www.SlipperOrchid.com, another hobby) - I did it as a weekend and evening thing mostly and in the first year turned $30k in sales. I had NO LIFE. Had I not been reinvesting so much into broodstock I would've turned a fair profit though.
Again, the key was finding items that I KNEW there was demand for, but also making sure there was enough EXPOSURE. I sold retail...sure I'd supply plants at a wholesale level but I did it only in BIG quantities...i.e. the comparison in the aquatic industry is that I wouldn't sell 6 fish to a retail shop, nor would I sell 6 plants to a wholesale orchid client.
I had a good selection, something that as a fish breeder can be hard to do. MOST of my retail sales were via eBay (and yes, I've actually purchased CORALS from vendors there, but never fish, there aren't very many posted to begin with); that got me great exposure...as an advertising venue eBay actually is one of the best out there for good ROI, but that's just my opinion. What would happen though is that folks would maybe win ONE auction out of the 10 or so I had listed, but they'd then ask what else I had to offer. "CHA CHING" as they'd say...they might buy another plant or two, or 10, from my website.
Another big thing that allowed SlipperOrchid.com to grow so quickly was that I focused on QUALITY...i.e. all my orchids were HAND PICKED from the area growers...you got the best of the 50 they had. Because I was hand picking from the big online retailers, I was beating them on quailty hands down. I started all my listings at a price I would be happy with, and when some of them sold for double or triple, well hey, that's what the market value was. So as a reseller quality was the kicker. It all came to a screaching halt when the orchids contracted a pesticide resistant strain of mealy bugs that to this day I haven't been able to fully eliminate. I shut down sales and haven't really brought them back online since then...once I have my orchids in a greenhouse vs. being an under-lights grower, I'll probably start sales up again...a few years from now at least.
Selling my offspring orchids, that was another matter. Often I had to drop my prices close to wholesale if I wanted to move everything I had fast enough. The difference here was that I had TONS of quantity but not much variety. Can you find 25 people a month to purchase 2 seahorses of a given species from you? Just a guess, but it MIGHT be difficult, especially at first. The reputation you build on those first crucial sales will be key, and if you let quality or customer service slide you'll feel it REALLY QUICKLY and the damage is difficult to repair.
The other downside (when comparing to a different "commodity" like orchids) is that folks don't usually have TONS of fish...orchids developed a lot of repeat clients whereas once someone has 2 or 4 of your horses, they may very well be done purchasing from you for several years.
I guess in the end, focus on quality, focus on fish that have high retail values and are in demand and find good sources. Deliver a good VALUE for the quality, and you're most of the way there. Go above and beyond for people and it will pay off (i.e. Dan @ Seahorsesource.com).
Marine fish breeding, at least for me and considering the current market, seems to be something that you should go into not really worrying about the profits, at least to start out with. Use what money you can generate to pay for your efforts and grow organically...don't quit your day job

IF/WHEN wild fish imports are reduced/eliminated, the tide will change dramatically.
Again, one last thought, get some good corals going as well...4 tiny frags of Woods Polyps, aka Giant Feather Anthelia, sold for $10 each to a LFS. Good Xenia cuttings around here can get $10 each too at our LFS's. Good GSP, you could probably never have enough if it's an exceptional strain. Heck, macroalgaes - I can't think of how many WTB posts I've seen for rufugium materials. Stomatellas (great little snails that breed freely and easily and can get you $2.50 a pop and eat all nusiance algaes). You could easily use breeding systems to raise both broodstock and these nutrient scrubbing organisms that not only cut down on your workload and salt use, but generate money themselves! Grow out Tridacna Clams from those cheap minis and in the process keep your nitrates way down...the ideas are really limitless.
MP