Security Bounties
Analyze software systems for security risks and report them for huge cash bonuses. He could likely report tons of them in a day, which would be way faster than a slow build up of religion. Then, he can work for private software companies or start his own security firm.
Microsoft pays out big time for security bounties, as does Apple, Facebook, Google, Mozilla. Your robot could bring in hundreds of thousand of dollars, or even millions, in a single day. Probably while walking down the street.
Since "He would prefer to keep a low profile and especially avoid government scrutiny, so anything overtly illegal is a bad idea." I'm suggesting the legal avenues of security bounties, since this is less likely to result in him being investigated.