Question: how iago manipulates roderigo to help him?
Answer: Iago uses whatever is within people to manipulate them. ... Iago works him by convincing him that his money (along with Iago's love) can buy Desdemona, a woman who cannot be bought. Iago exploits Roderigo's prejudice and his passion by continually telling him to "put money in [his] purse" and to follow Desdemona.