Hello, everyone, I have a character who runs into teens that live together in the leader's house and steal for a living. The protagonist impulsively aids them in the robbery, and then realizes that the fulfillment he's looking for could be in joining them in their schemes. They reject him at first, simply because they don't trust him right away and because he would be another mouth to feed. What is something the protagonist could do to impress them and convince them that the protagonist is a necessary force in their lives? An idea I had was for the protagonist to, by himself, rob a house the gang had targeted before they could. I am just not sure, though.
The trick here is that doing things unprompted is more risky than useful. A house of criminals like a military runs on protocol. It's how they survive. A military is more likely to brand someone's pushy attempt at getting in as more of an enemy than an ally. If the issue is simply trust(how do I know you aren't a cop?) Than that can be overcome by time/a situation a cop can't be in. The bigger issue is that he would be another mouth to feed. This implies he can't pull his weight. In this regard. He either can or can't. If he has to prove himself. That is fine. If your looking for ideas on how he can prove himself it really depends on the criminals. The military anology should be true to some degree. The more true it is. The more unlikely they are to like outside help. At least in my opinion. So if the rules aren't harsh. I could easily see someone wanting to use his eagerness essentially for free but the point there is it provides your character a chance to prove himself. Because once he has. Then they should want him.
One of the classic ways to get an outsider in is a rare and essential skill, and one of the rare and essential skills is medicine. Simon Tam in Firefly, for example.
Maybe someone else vouches for him, such as a relative already in the gang, or someone he's individually impressed who argues to the leaders that this kid is worth giving a chance?
In real life, he/she would need to prove themselves repeatedly- feed them easy jobs, be there to help them escape a sticky situation, always show up when called upon, introduce them to a different fence, etc. It would really work like any other group/organization.
Make him an x cop with all the skills of evading police. Give him special radio frequencies to scan if the police have been notified about their operation. Give him a test that a cop would have to turn down, such as a hit of cocaine or sex with a willing member.
I know cops that do stuff like this unsolicited and I doubt anyone would be willing go give up some of their stash to someone they don't really want around and who they've already trusted enough to help them in one robbery. Personally I would have them leave to do a job without him, and he follows. Things go south and they're all running with a bag of goods. The cops corner them. He's all like, "I'm just an innocent bystander!" The rest of the gang is all, "WTF, mate." And the cops just go, "Prove it." So he grabs the bag, hands it to the cops and everyone escapes while that's happening. The cops let him go because he's obviously not helping them and historically hasn't been seen with them. Then he goes back to the clubhouse and they're all ready to murder him, but then he's all, "Ha ha, you fools. I switched bags out while your back was turned!" then the gang's all like, "Yeah, I guess you're alright." Boom. Second chance.
A bit out there, but: They doubt his ability (and don't trust him) so turn him away. He comes back and robs their base, taking something of high value and replacing it with a note that directs the gang to a location where he's waiting with the item and willingly returns it to them. The leader looks like he wants to kill him but then turns around laughing and says something like "you're one crazy son of a bitch, you know that? But you've got balls. I like that. Alright, you want in? You do something for me first..."