By the time you graduate from college/university...
With respect, as everyone has different goals and approaches to life... I would run the opposite way from this advice.
In life, you can always wait longer. You can always put things off. You can always do them later.
Do it when you're young, but be okay with doing it a little bit wrong. If you have a passion for something, do a smart amount of basic research so you're not being foolish, and then just jump in.
The person you will be when you graduate college is completely different than the person you are today. I think older people often forget how fast your life changes in a year when you're young. 15-21 is like the difference between 21 and 51.
If you are passionate about something, don't put it off, pursue it today. Pursuit of it will shape the person you become. If you put things off, the only person you become is someone with shifting goals of what you used to want and never gets to have any of it.
When you're 20, if you want to backpack around Europe, do it, not in another 10 years on a prescribed 2 week vacation when you have lots of money. If you want a PS4, buy one now. Not in 5 years when it's 1/4 the price and no one gives a crap about the games you're playing. If you want to have kids some day, have them, don't wait another 5 years, another 5 years, another 5 years, because it always is the smart thing to delay gratification and delay the things you want.
Having a long term project on a low wage is a fantastic thing for someone your age. Rather than blowing your money on stupid stuff you won't care about, and working a job you don't want or care about, you'll go into work knowing why you're there, and what your money is doing, and what you're working towards. Going home and tinkering on a project will add probably the only long term anchor you have in your life that you're not doing because you're obligated to do it. You probably haven't had much of that. You have to go to school because you have to. You have to go to college because it's foolish not to. You're too young to be married or have kids. You're going to have ups and downs over the next while, and having something solid that you progressively move towards is a valuable thing. Failing, succeeding, or learning at it will change who you are. It won't feel like a change, it'll just feel like you're the person you want to be, but that's just it. You'll be the person you want to be, not wake up one day and wonder why you're the person you won't want to be, which happens to a lot of people.
I can't think of a single person who's doing what you're planning on doing (generally), for whom it wasn't a defining point of their life.
The advice I'd give you in terms of goals, is to ignore performance. You're not a racecar driver. Your first car is going to be a piece of crap. In fact, you're going to have to build it just to be a piece of crap. With electric, you can always upgrade it later.
- What range do you need? I.E. Below what point are you going to think "This is stupid, why do I even have a car then?" Start at that baseline.
- Buy your batteries last, they're probably the most expensive part, prices will drop and availability will go up.
- Don't pay for any induction motor new. Either buy an OEM motor from salvage, or go with a forklift motor for super cheap ($0-$200). Motors are just about invincible, it'll probably outlive you.
- Consider whether you'd rather be driving a crappier car sooner, for cheaper, and upgrade as you go. Because that's probably an option.
Anyway, that's my two cents.