House geckos are small and you could keep a pair in a ten but they are harder to breed. Ok, scratch that, they are easy to breed but getting the eggs to hatch and keeping the babies alive is a pain in the butt.
You might look at Texas Banded Geckos or Tuscon Banded Geckos or Central American Banded geckos. All of these guys are small enough where you could keep a pair in a ten. The Texas Bandeds are small enough to keep a trio in a ten. CA bandeds are pretty easy to breed, but the texas bandeds and the tuscons are a little harder. Whether you can get a pair for under 40 bucks, depends on the particular show and time of year.
It might be better to wait and save more money before looking OR just get a single gecko for the time being, enjoy it, let it grow up and then get it a mate. Babies are usually much cheaper than adults but it is not recommended to keep babies together. I can tell you that breeding is fun, but it can be frusterating and EXPENSIVE. Yes you can get a pair of _____ for under 40 bucks. You might be able to keep the pair fed on your slow but steady income but let's talk about the breeding costs themselves. First thing, you will need an incubator. A hovabator costs around 39.99, give or take depending on place. My advice is to get one at least a month before eggs are due so that you can get the temp stabilized. Next, the eggs are going to hatch. You can't keep babies together. So you will need to figure caging and heat for them. A simple rack system will cost 100 to 150 bucks. Usually they don't come with heat tape. Or you can go with separte shoeboxes but you still need to invest in a heat source for all cages. Next comes feeding the babies. We'll be optomistic and say that you get 8 eggs during the season and you get all eggs to hatch. Depending on species, you have to find the appropriate sized food for them. This can be a pain if you are looking for really tiny food. Once you get them all established you have to figure out what you are going to do with the babies. Don't plan on selling them to ONE store. I can tell you from experience that Pet stores will take in only what they think they can sell. They may tell you "we'll take all you can produce" and actually only take two.
I'm not trying to discourage you from breeding geckos but you seem so fixated on cost and concerned about room that I don't think you are ready for breeding geckos. No matter how prepared you think you are, you are never prepared for the actuality. 17 baby geckos SOUNDS cool and easy but can be frusterating and overwhelming. Especialy if you are on a limited budget. Let me give you an example: This year my roomie was given 7 adult beardies. Oh cool, we can breed them. Currently there are 50 baby beardies sitting downstairs in tubs. Wanna know how much it costs to feed them each week? Actually, I don't want to think about how much it costs us.
My advice is for you to get one gecko, keep it as a pet. Learn from it, enjoy it and in a few years, shoot for breeding.
