Let’s try this again.
Fish are out. And apparently flowers are out, even if they aren’t in anyone’s yard. 
Labour.
Trying picking up salvage from trash day, it got so bad in my old neighborhood in Houston on trash day there were trucks prowling the streets before trash day. I put a old and big but working monitor on the curb, it was gone in twenty minutes!
Huckleberries, salal, fiddleheads, bear grass, devil’s club, mushrooms, ginseng, usnea…
A word of caution: (1) You are still going to need to get a permit. (2) For every one of you, there are a hundred Mexicans and El Salvadorians willing to work ten times as hard as you, in worse conditions.
water
How about… diamonds! Just find yourself a piece of land in Africa and get to work diggin’
Air. You could buy a bunch of balloons to store it in.
Do you mean like the people who take the tin cans and cardboard out of people’s recycling bins before the municipality has a chance to pick it up? If so, that’s theft just like stealing plants from the roadside. The municipality counts on the value of the metal, cardboard, glass and so forth to partly subsidize the cost of the trash service.
grass, the number of grass plants sold if really large.
On the other hand, you can make a fortune by legally collecting waste paper and cardboard. Zhang Yin is a Chinese woman who started to do this not that long ago and amassed a fortune in the billions.
Yanno, seeds are cheap. Really, really cheap. You can grow your own, in your yard, your friend’s yard, a community garden, whatever.
I think a political lobbyist would have more insight into this than anyone here.
Petroleum. Just dig in the right place.
Have you ever thought, instead of wandering around looking for random crap that you can collect and sell, how about creating stuff?
Like, you can wander around looking for plants that nobody wants and trying to sell them, but those are, you know, plants that nobody wants. So it’s going to be hard to find people who want them. If you want to sell plants, you could grow plants that you know people want, and then sell those plants.
Reminds me of the old joke. Two economists are walking down the sidewalk. One of them says, “Look, a $20 bill lying on the sidewalk! Let’s pick it up.” The second economist says, “Don’t bother, if it was a real $20 bill someone would have picked it up already.”
See, if there were large amounts of things lying around that you could legally collect with little effort and sell for good money, there would already be people doing that, and pretty soon there wouldn’t be any more of that stuff lying around. People do come up with new business ideas all the time, but those business ideas are a bit more complicated than “Wander around looking for stuff to collect and sell”.
@Lemur866 - the OP obviously subscribes to the Sanford and Son school of economics.
Your Mum.
I wouldn’t recommend digging up plants from the wild because you can get in legal problems if you dig up plants that are endangered or otherwise protected. And of course digging up plants from people’s property without permission is also asking for trouble. Plus a lot of what you find in the wild wouldn’t make a good garden plant anyway.
Flower seeds are really cheap and you have all summer to grow them. Figure out some easy to grow plants that you think people will buy, get some seed packets and start some seedlings right away. Once you have some decent sized plants you could try selling them at a garage sale or on craigslist maybe.
If you wanted to sell cut flowers, you could start some zinnia or cosmos seeds and have flowers in a couple of months really easily. Those are annuals though so you’d have to start with seed again next year. You can save the seed from the flowers this year though so you don’t have to buy more seed.
What about rocks? You could go down to the local river, pick up a few rocks, glue some little googley eyes on them and sell them as companions to lonely, lazy people.
How about dirt? Go down to the local river, fill up a bucket of dirt, dry it, clean it, and put it into cookie cutters and sell them as “dirt cookies.”
What about pond scum? Go down to the local river and collect some scum off of the river rocks and piers and boat ramps, etc. Arrange them into decorative patterns on sheets of paper and sell it.
What about old electronics? Go down to the local neighborhood and ask people for their old cables, computers, monitors, or any other electronics they want to get rid of. Sort them and glue them together to make little electronics figurines/sculptures/dolls, etc.
Try all of these and come back to us with your results.
have you considered just looking for a job instead of some mythical item that is just lying around free for the taking and yet at the same time worth money?
IF you’re sincere (most of your other threads sound like trolling), another vote for working for your money. I think you’ll find that once you find, process/fix up salable items, market and distribute them… you’ll spend so much time that your hourly “wage” will be below minimum wage.