iPhone 4 16GB (GSM factory unlocked!) FOR RENT

I have an iPhone 4 black 16GB (in fantastic condition, purchased in March 2011) which I won't be needing till December 16. The phone is purchased from overseas, so it is factory GSM unlocked (i.e. it came unlocked at the point of purchase, not jailbroken) and can be used with AT&T, T-mobile or other GSM carriers. I am willing it to rent out the phone till December 16, for $40 a month.