Step out of line and we cash you in for insurance.
Hello! In an American crime drama, a policeman works undercover. A mysterious female caller: "Hey pretty boy, I've been hearing stories. Word on the street is you've got skills. We've got a contract for a boy like you. No questions asked, big payoff. Step out of line and we cash you in for insurance. Do you know what I'm saying?"
Could you, please, explain to me what "we cash you in for insurance" means here?
EDITED: She's offering him a job. The contract is for him to steal an expensive sports car. By doing so, the deep undercover policeman proves to be "legit" and becomes a member of her gang.