Possibility of payment for depends on your state, your local chapter, your clientelle, your experience, your services, etc.
My state really frowns upon getting paid for checking seats because our governor provides us with some pretty great grant funding. It was a struggle for me to get the unofficial OK from my instructors & the state coordinator when I wanted to charge pregnant mothers' insurance for a medical office visit when I educated them on child passenger safety during child birth classes (or at home for moms on bedrest) at our Women's Clinic. That was a small niche of the population & I was also volunteering at our refugee center for free.
Now that I don't have that niche audience, it wouldn't be right according to our local unofficial rules of CPST ettiquette to charge the general population. I do volunteer with our daycare council to provide low income & teen parents with the education + carseats they need. I myself am living below the poverty line as a single mom & full time college student, but any $ given to me for a seatcheck is forwarded on to SafeKids or the NYS governor's traffic safety office as a donation to help keep getting techs (re)certified, to pay for the grants for carseats/supplies, etc. Eventually, I do plan to apply for Instructor candidacy & then I'd have a chance to earn some $ as a tech.
Bottom line, it's important to remember that we're not here to provide a service: we're here to educate :twocents: