If you already have a 6-figure income, I'd suggest being content with that.
You ask how big a shop is needed to gross $100k+?
I'd suggest a customer base and your own design abilities and skills are needed, rather than shop floor-area of whatever square feet or metres.
The roof area of the workshop does not dictate ability.
Plus a demand is needed.
I'd suggest a 2nd hand Universal laser be considered.
Software learning curve is so simple.
We have a ULS and two quality chinese systems.
The little ULS with the RF tube gives small item quality, to way exceed what the CO2 tubes in the two great chinese systems do
.
Best wishes,
Ian
ULS M-300, 55w made 2002 with rotary. Goldenlaser 130 watt, 1300x700 made 2011.
Flat bed 2500x1300 150/90watt 2 tube laser, 2018 model.
Esab router, 1989, 4.5 x 2.0 m, conv. to Tekcel, and modded a 2nd time.
HP L260-60". Roland PNC-1410. Mimaki GC-130 SU.
Screenprinting carousel 6x4 and 7x4 ft 1-arm bandit vac table.
Corel Draw X3, Illy, Indesign & Photoshop CS2 & CS5, Enroute 4
Pencil, paper, paintbrush, airbrush & dagger-liners & assorted other stuff.