Salary
Average Salary: $29,600
Expected Lifetime Earnings: $1,235,741
As far as entry-level careers go, subs don't make a bad salary. Of course, they don't make a good salary either. Typically, they're paid for every day they work. The average varies greatly from school district to school district, but that daily pay range goes from about eighty bucks on the low end to $200 at the high end (source).
If you're working as a long-term sub, you can look forward to a slightly higher daily rate. This leads to a nationwide average substitute teacher salary of almost thirty grand per year (source). But you'll have to have established yourself as a reliable sub day-to-day before anyone's willing to let you teach for an extended period of time. For some reason, schools are pretty particular about who they let near the kids (go figure).
There are some ways to boost your pay if you're able. Frequently, big districts will pay a higher rate for fully credentialed teachers who are willing to sub. Typically, these positions will be filled by teachers in between full-time teaching jobs, or retired teachers. But if you've got the qualification, you might be able to earn a little more.
But keep in mind that this varies by a lot. You could be working every day and pulling a livable wage. Or you could be getting a call twice a month, and spending your time sitting nervously by the phone. You never want anyone to get hurt or sick, but it sure helps you feel better when they do.