Tell ya what. Go to your local dog park. Offer to clean up all the poop in little baggies, as long as you get to keep the poop.

Then come home with hundreds of baggies of dog poop, and set up a little lemonaid stand. Except instead of lemonaid, you can sell dog poop. $0.25 per baggie.

Report back how many you sold just because it exists for sale.