It's a matter of scale. How many teenagers do you know who make $5 here, or $10 there, just mowing lawns, cleaning windows, or doing babysitting?

They're making money without luck, without scamming, and without being terribly valuable.

The problem is those things don't scale. I can imagine a couple of happy teenagers raking in $400-$500 a week, if they really push themselves, but it will be very seasonal work.

Hrm. uber for lawns? facebook for windows? (There are a lot of agencies that work as middlemen for childcare, where often vetting and background checks are involved. I'm not familiar with such a thing for pet-walking, window-cleaning, or lawn-mowing. Perhaps they exist, or perhaps there's your cheap and easy idea! Physical labour is cheap, anyway :)