Safe Investment Strategy?

What would you call something that works like this?:

1. A company asks for an investment of money, with the promise of returning your principle as well as a guaranteed rate of return.
2. Investors get confidence by seeing the returns, and if any of them tried to individually exit the investment scheme, the company would be able to pay them out.
3. The company used that confidence in order to convince investors to leave their investment with the company.
4. The company could only continue paying out returns for so long as enough money keeps coming in to cover the guaranteed rate of return.
5. If every investor tried to take their investment from the company, the company would go bust.