My vote is for a 55g FW
setup, which would allow you to keep many of the nicer looking FW
fish. You don't think you will get one because of price? If that's the case, have them check out the 55g kits at WalMart. You should be able to get everything you need for around $150-175 and a cheaper stand is $100 and they work well.
You won't be able to breed any SW
fish and not most FW
fish with that small of a volume of water. For breeding you generally need lots of space, tanks, and money to get started. If you are interested in making a decent amount of money I'd highly suggest that you get 3-4 TEN GALLON tanks. You can make a stand or find suitable stands for all of them or for each of them individiually since they'd weigh about 110lbs max each. In each of them you could house a different type of shrimp. You could keep red cherries in one, yellows in another, snowballs in another, and blue pearls in yet another. Then, you could also put tigers in with the blue pearls, blue tigers in with the red cherries, crystals reds and crystal blacks in with the yellows and I'm sure you could find something (green shrimp?) to put in with the snowballs. In addition to those you could have assassin snails in a couple of those tanks, and a different type of snail in the other tanks.
The beauty here is that you are in a decent climate and you could get by with no heater in the tank and you won't need a light either since you could put java moss in each of the tanks. You don't even have to run filtration but if you did want to I'd recommend a sponge filter for each tank. You could easily have a $10 pump run all four tanks. I would suggest glass tops for each of the tanks though to prevent jumpers. You are looking at about $15-25 for each tank depending on how elaborate you want the setup to be. The simpler the better though IMO
. You most costly item will be the shrimp. You could start with a dozen each of red cherries, yellows, blue pearls, and snowballs and you would spend about $100 total. You'd make that money back in little time however and they are lots of fun to watch.
And you WILL want heaters once you venture into CRS/CBS, tiger shrimp, and other caridina sp. It'd be a shame to lose a tank full of hundreds of dollars of shrimp because you didn't purchase a $5 heater.