My mom said that I could live with her until I die as long as I do my chores, but I wouldn't do that to her lol.
Even though it's hard to mix school and work, it's not nearly as hard as some people think. Most people want to jump right into a full-time job immediately, which is perfectly fine, but that tends to bite them when they realize they actually mean full-time. I'd recommend starting off small, getting a simple part-time job and maybe some volunteer work. You won't be nearly as overwhelmed working 2-3 days a week as you will working 5 days. Trust me, my brother decided to do full-time while he was in school, and he would come home at 11 pm and go straight to bed, and he was always tired, no matter what.
But hey, that's just me. If you can fit a full-time job into your schedule, go nuts. You get paid more.
Now, when should you have a job? I was raised to believe that you get a job at 16 while you're in school, but I don't know how others were taught. I honestly think your teenage years is a great time to get a job, provided there's nothing else holding you back. If you're 16 and you spend about 5+ hours at home doing absolutely nothing, give or take a few half-hours, get a job. What's so bad about it? You get paid, what could possibly be bad about that? Well, unless it's illegal money. Don't do drugs, kids.