Charly and Bob above have it wrong.
" If he gets 10% interest from 12,000,000 He would get 1,200,000 a month! "
No, you wouldn't. Interst paid is quoted on an annual basis, not a monthly one so it wouldn't be 1.2 mil a month in the above example, it would be 1.2 mil a YEAR.
"But lets say you have 100,000. you would get 10,000. but I don't think banks give you that high interest."
That is correct, but again, it's annual, not monthly. And no bank currently is paying anything NEAR 10% on any kind of demand deposit (ie "Savings") account.
The way it would work out is as others here have suggested, by receiving 1 or 2% interest, your friend (or you, for that matter) would receive $10,000 per million for each interest percentage point on deposited money per year in interest payments.
A better and safer way to go would be to buy ten year US Treasuries which currently pay a "coupon" payment of 3.5%. That would be $35,000 per million each year in interest payments and if you held the bonds all the way till they matured in ten years you would get your $12 million back.
Series 7 General Securities License holder