I really don't mean to be rude, and probably should keep my opinion/comments to myself, but I just can't help it.
"High school"
"No money"
"Friends that can work on it real cheap" (Nope, there's no such thing on a Tesla)
It just sounds like at this point and time, a Tesla is unfortunately not in your near future. Even if you do find one in that price range (you won't), it will be so beat up, it will cost you a fortune to fix anything, and will not be a good Tesla experience.
I am glad that you want to go EV, may I suggest a lease on a Bolt, or the 20k budget will also get you into a very decent i3 (just make sure that you get a rex). Those are amazing cars in that price range.
Another option would be to have someone cosign for you on a lease, and you'll be able to get into a brand new, loaded Tesla for around $24k for 2 years. And do take into account that insurance, at your age, will probably be hovering close to 400-500 a month, and that whether you buy or lease. Or ultimately save that 20k for a down payment on a 3, should make for low monthly payments.
Good luck in your search, do keep us updated.