I mean when I started working there wasn't open source as such.
Maybe the local computer club or some rich guys that could pay for BBS connections exchanging stuff.
Everything from hardware, text processing, drawing, music, compilers, editors,..., was provided by proprietary overlords.
I too perform work for enterprises, getting payed to work with and in all things Linux, Java and Python.
Just because its freedom software doesnt mean there is no money to be made or make.