I once had a buddy who was sort of a generalist pro photographer. His absolute favorite type of job was the big company executive headshot day. He'd spend a bit of time setting up his setting or background, light everything well, and then just essentially have them come in like an assembly line and get their pictures taken. He'd typically get around $100 per delivered shot. Which is to say that these pictures aren't accidental; a lot of care goes into them. I'm sure that's somewhat apparent, but it might be more work than you realize.