Found!!! Specific Fic: Dean sells himself for money
First of all, I've gone through the tags and for the life of me I can't find this story anymore. It's a Teenchesters story. Dean sells his body to have enough money to take care of Sam. In this story Dean was somewhere outside in the woods (?) or at a remote area to meet with an older guy who wants to have sex with Dean. I can't remember if it was Dean's first time hustling. I vaguely remember that the guy ws pretty rough with Dean or did more than they originally agreed on. I think that the act itself took place on the hood of the car (the guy's car?). Sam was close by the whole time (think he waited in the Impala) and even though Dean instructed him to "play bossom", Sam still looked and saw what was happening to Dean. After the act, Dean feeling humiliated, the guy noticed Sam somehow and was about to attack Sam and grabbed him (not sure). That's when Dean went apeshit. It was a classic case of Dean taking a lot but don't you dare to ever mess with Sammy situation.
I'm aware that this is all pretty vague. Must have been five years ago that I read this. Any help would be greatly appreciated.