10 for 12!!!! High yield

I recently had a young man come to me and ask for my opinion about a small house that he was interested in leasing in a nearby city.  He told me that the owner was asking $1,200/month rent and an additional $1,200 for a damage deposit.

After we determined that it was a fair price for the rent on that property.  I told him to ask the owner if he would take $12,000 for a one year lease and waive the deposit.  He told me that the owner wouldn't take it.  I asked him how he new that. Answer, he said he wouldn't take anything less.  Also he told me he didn't have the $12,000.  Answer, don't tell the owner that.  First get the deal and then we will work on the money.  

He called me the next day and said that he would indeed take the $12,000, waive the deposit and would write it into the lease to do it again the next year at the tenants option.  I love America. 

To solve the money problem, I loaned the tenant $12,000 at 10% interest with payments of $1,046.27/ month.  Who won???

1. I made 10% on my money for a year.

2. Tenant saved $153.73/month and didn't have to put up a deposit.

3. Owner eliminated the need to worry weather the rent would come in next month.

WIN, WIN, WIN

How did I know that the offer was a worthy investment?  Anytime you can buy a stream of 12 monthly payments for price of 10, your yield is 35.07%.  You can borrow on your Discover card and pay back the same way at 13%?