It is a GREAT idea. Wonderful concept.
And it is also illegal in many/most? states.
Due a lot of due diligence about the legalities of this strategy.
If you are really 21, you may not be aware of how crazy it was 5 or 6 years ago. Many people were doing similar things.
Some of them were not ethical or clear enough on what they were doing.
Some "poor little guys" were "robbed" from their houses cause they did not understand the legalities. Went to court. Sue the investor (in this case, you). Investor goes to jail. "Poor home owner" gets the house back.
So, again, check the legal aspect of this in your state.
Also, you don't get the equity until the owner buys back the property. If the owner fell behind then his/her credit got ruined. Good luck having them qualify and get a new mortgage to buy it back in a short period of time. These days banks want spotless credit history and higher downpayments. The owner, by having owned a property recently, wouldn't qualify for the FHA programs that are allowing a lot of people to get loans with 3% downpayment (first time home buyer programs, etc).
I commend you for thinking this way. I am sure you will be very successful. You are finding solutions to current problems.
I hope you find a way to make this --or something even better-- work for your customers and investors, so you become rich while providing a great service.
Again, do not want to discourage you, so make sure you read about "anti-flipping" laws in the states you are planning to invest.