I need help! Is this legal?

[Jordan Harris]

My sister found a home she likes but can't afford to pay the down payment. If I agree to buy the house with her (she and I are on the mortgage together), will that allow us to only pay 5% down? This is confusing because this would be an investment property for me (usually 20% required), but my sister is going to live in it (3-5% required).

From there, I pay for all house repairs. My sister pays the mortgage, plus $300 per month (cashflow) to me. Essentially I'm renting a property out to her that she and I "bought" together. Is this legal?