Not sure what you call “first” so I’ll list them all, up till my present one:
at 12, I was babysitting (lasted all of twice, then I gave up)
at 16-17, I was worked in summer camp
at 17, I did a one-week stint in a take-out food place
at 18.5 I started working full time (whse work first, then became a numbers cruncher, once I got my degree)