Hi Lisa
Before you buy equipment, I'd suggest some training first. You will then have a better insight into what you'll be letting yourself in for. Also, much commercial work, esp. carpet tiles and CGD, will be cleaned with different equipment to Mrs Smith's lounge.
Depending on how your business plan looks, it still may be advantageous to continue with a good subby.
The NCCA in Leicester have a course due any day now. Prochem in Surrey have regular courses plus various others around the country.
Safe and happy cleaning

The Ken