I, like many others around here, run my entire studio setup with OS9. Since I actually DO get a trickle of performance and ASCAP income from past work, I can say that more or less qualifies as a "part of a living". HOWEVER……
I have in the past run an entire video projection sales and service business in OS9.
I used Filemaker 4 as the customer, inventory and labor database, Canvas for tech drawings, InDesign for invoice and form layout, a contact manager I can't remember the name of and a few other apps for various needs.
I started that on an SE30 with an Imagewriter II (to print multiple-copy invoices) and a 40Mb HDD.
Trust me… you haven't lived until you've had to create tech drawings and full-page forms on a 7" B&W screen. One of the happiest days of my life was the day I acquires a (256) color video card to stuff into the PDS slot and a 19" color monitor. I felt like Dorothy when she said "We're not in Kansas anymore, Toto".