After being in your shoes years ago (young, not a lot of experience or money) and trying to break in, I'd suggest starting in karts. And in those, a "stock" engine class. No racing is cheap, but "stock" engine karts is about as cheap as you can go and still run a vehicle that is designed for racing. A UCar may be cheaper to build than a kart, but it also requires a full sized tow vehicle and trailer. You can put the kart in the back of a pickup truck or even the trunk of a large car if you want.
Legends cars are a handful to drive, and really tough if you don't already have some racing experience. They need to be set up almost perfectly or they're uncompetitive, and slight bumps can require parts replacements or even frame straightening / clip replacement. They control the parts sources so you either pay full retail or take your chances with used stuff.
If you decide to try a kart, you don't have to buy a brand new chassis. However, don't buy one that is more than five to seven years old because their technology evolves quickly and because the chassis are designed to flex - which also causes them to fatigue. Don't buy a kart that has had a serious wreck - find somebody you can trust who has karting experience and who won't profit from the sale to look over used karts with you and help you make a good decision. Expect to pay around $2500 - $3000 for a new chassis, $1200 and up for a good recent used chassis.
For "stock" motors, I put that in quotes because most of them actually are modified somewhat. Some tracks have a "Predator" class that is truly stock (governor and all) but there are Predator classes that allow some modifications too. Usually the "clone" classes are slightly modified. The deal here is that unless the motor is box stock you'll need motor building experience before you can modify your own motor legally and effectively, but you can buy motors from an engine builder. A truly stock Predator costs around $99 (with coupon) at Harbor Freight. A "clone" will cost $600 - $1200 depending on who built it (still talking "stock" engines here) but to start out you don't need a $1200 engine. A modified Predator costs about the same as a clone. There are other "stock" engines raced too, so before you buy anything you should pick a track to race at and ask them for their rules etc. Since you are 14 they'll probably place you into a Junior class, and that class could specify a certain engine as well as a certain sized restrictor plate.
You'll need some other parts and tools too, depending on class rules. A good place to get more information is the karting forums on 4cycle.com.
Best of luck, and hope to see you at the races!
