He didn't know it was a scam when he signed on. Stocklein asked him to and he was supposed to get things with the SEC cleaned up so they could go forward and continue trading. What they (UC and Edwards) did was stonewall him and provide little, if any, information to him. As we now know, there weren't really any financial records (that is why the auditor quit) and they kept promising information to Mahey which they never provided.
Why Would Maheu get involved with a Scam in the first place at his age?
He worked with Stoecklein regularly, and some of the companies (and the people, like Tony DeMint, who was part of their company) weren't exactly pure as the driven snow.
And yes, I think he probably did need the money. Or wanted it, at any rate.