Cheapest service to unlock phones?

Hi! I'm making money flipping phones from USA to my country, I've been buying unlocked phones but I saw locked phones are cheaper so buying locked phones and paying to get the unlock code may cost less than buying the unlocked phone.

I want to know if someone knows any website that sells cheap unlock codes (android phones)? Thanks in advance!

Just search ebay. A lot of good sellers for $1 per unlock.