Great ideas although I find writing 20 articles in a day too exhausting. Similarly, I doubt if you can collect aluminum cans in one a day that you can sell for at least $100, unless you will do it with other friends and colleagues. This is a good idea for a fundraiser, though. On the other hand, I would recommend baby/dog sitting or house/yard cleaning.
Sell scavenged valuables. If you have a metal detector, or even just a good eye, go to public places where people are likely to drop something unnoticed (such as parks, beaches, and shopping areas), and look for money, jewelry and other valuable goods. This method isn’t very reliable, but you just might get lucky and be able to find something you can sell quickly for cash.

Tenants sometimes damage properties, and depending on local laws, they may be hard to get rid of. You'll be the one they call in the middle of the night if the roof is leaking, and you'll have to clean and perhaps freshen up the property between tenants. You can outsource much of this to a property management company, but it will take a cut of your income, often about 10%.

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