If he likes security, there is a need for security systems that don't spy on their users. People don't have the time and resources to look for the available off-the-shelf systems that value privacy.
This is something that he could easily start small with, even just doing it on weekends and evenings while working some part-time job, if that's needed.
Aside from installing tech, he could do security evaluations, which would teach people where their weak points are, and what needs to happen to harden their location. This would lead to sales for hardware and installation. Offering kickback for successful referrals would help drive happy customers to bird-dog for more.
Hosting a free class about basic security could get the ball rolling quickly.