I currently only work for 1 photographer as a lighting tech but in the past have worked primarily by referral through photo agencies.
I shoot as well but assist 75-150 days a year. Over the last few years it’s been less labor and more money. Lots of tracking down incident angles and adding gradients in surface.
I make 450 for editorial and advertising base is 750-1200/day. Prep days and travel are full rates. Business class if flight is over 3 hours .
Editorial assisting is usually a noon call time. Load in. Find the frame. Shoot subject and load out by 3.
Advertising jobs is a prep day going over the deck and making EQ orders, scouting the location and path of sun. Shoot day is always a solid 10 hrs with 2-3 OT. Typically IBM, Apple and Google jobs are 5 day jobs total with 1-2 being shoot days.
For my best paying job I was supposed to go to Bulgaria for 8 days. Job confirmed and then something happened and the creatives pulled the plug. I got paid full rate for cancelation.
Worst paying was a 3 day job and the week after it was shot and rounds of retouching were being approved agency went radio silent. Turns out CEO was taking money from the company and they had to shut the doors mid project. Job never paid out.
Shoot what interests you. 17 years in fashion was brutal and boring from a personal stand point. Now working in science and technology and talking to engineers is so much more fulfilling.
Know the value you bring to the table. I’d say 75% of agency photographers would be lost without their first. Assisting is a thankless job that’s hard on the body and at the end of the day it’s the center of advertising work being produced.
Also take the time to really understand how light works. The different qualities of light and how that relates to shape and texture of the subject.