I do think its a good idea, its a wonderful thing to try and help sick animals! but not at your age... unless you have a very steady and high income, there is no way you can come close to paying for the supplies, UV lights, cages, food, not to mention vet fees and medication.
Don't forget that you won't be able to keep 2 animals near each other until they've both been given a clean bill of health... that's a lot of room in your house to take up for jusst one sick animal!
Also, you mentioned the only thing you would take would be small lizards and a couple smallish snakes... unfortunately those rarely need rescuing. They are relatively easy to care for and dont take up much room, and so people dont often get rid of them just like that.
You'll most often see burms and retics, and green iguanas. Some torts, crocs, caimens, etc. All of these need a LOT of room... more than you could imagine! It isn't really fair to say "well, i can keep this rainbow boa, but not this burm" or "sure i can take this leopard gecko, but sorry idont have room for a green iguana". I know you arent in this to get free animals, but you are expecting to recieve animals most people dont just give away.
When you're making lots of money and on your own and established (not getting ready to move out or go to college as you will in a few years), have a wife that likes reptiles, then you could get to building a facility and taking in sick animals that really need rescuing - the burms and iggies. For now, though, I'd suggest you volounteer a other rescue agencies... that way you could provide homes for animals you CAN house (they sometimes get in smaller animals that you could take), and you'll be devoting your time to an already-established rescue center that will really appreciate your help (they need it!). Or even the humane society! Doing that, you'll pick up skills, legal tid bits, license info etc that you can later put to use when you can afford (in time and money) to start up a rescue center that can take in the animals that really need rescuing.
Oh, another thing that desperately needs doing is straightening out petstores! yarg. You could visit petstore in your area and try to improve the conditions in them. There are some great articles written up in these forums that will tel you the best way to go about making a difference. Even if the biggest change you can make is convincing the store to cary caresheets to give out with animals, you'll still have made a difference.