This is one way in which the scheme could work:

1. You put your own property (home, car, piece of land) as a collateral and get a loan from a bank. You can also try to use the purchased property as security, but it may be difficult to get 100% loan-to-value.

2. You use the money to buy a property that you expect will rise in value and/or provide rent income that is larger than the mortgage payment. Doing some renovations can help the value rise.

3. You sell the property, pay back the loan and get the profits. If you are fast, you might be able to do this even before the first mortgage payment is due.

So yeah, $0 of your own cash invested. But if the property doesn't rise in value, you may end up losing the collateral.