Know your market. Starting with small homes? Large homes in your area? Going after commercial?
I started with residential only. Typical home was 1200 - 2000 sq. ft.
Truckmount and Water Claw or other extraction tools
2 medium LGR type dehus
12 air movers - mostly centrifugal but some radial as well
Training classes - WRT, ASD and something to help you market. Maybe the Restoration Strategies Turbocharged class or Build a Better Business; Sooner or later Strategies for Sucess.
Meters including hygrometer, pinless and pin type meters of good or better quality
Thermal camera if you can afford it.
Package can be $10,000 to $20,000 if you already have the truckmount; considerably more if you need the truckmount.
Money for marketing or at least a lot of time devoted to marketing. Most areas are rather heavy with competition.