Salary
Average Salary: $22,320
Expected Lifetime Earnings: $931,815
We'll be honest with you: this job will never have you rolling in dough. The median salary for a janitor is $22,320, and it caps around $37,000 (source). Unlike other careers, where you might find room to move up the ladder and increase your wages as your experience grows, the janitorial profession is pretty lateral.
Since your salary won't be very big, you might want to consider joining a union, just in case your employer decides to try to take a chunk out of your paycheck or your benefits. Your union might even be able to help negotiate a pay raise for everybody.
Just as tides lift all boats, unions lift all paycheck numbers if they win a suit against the employers. You won't get a personal raise, but you'll probably be too busy counting those extra bucks to care.
Short of setting your union against your employer, your best bet for increasing your cash flow is taking on extra shifts or working at additional job sites. So long as you're able to keep everything clean and tidy, your employers shouldn't have a problem with you working at another place. The one thing you'll want to watch out for is burnout. Spend all day cleaning toilets and your good mood can end up...well...in the toilets.