Yes, you can start with one user license. You can do all that is required in order to manage your company. No need to pay for the number of staff. A flexi user can get access to all the modules that you have purchased like accounting, HR, payroll, CRM, purchasing and POS (depending on the modules/packages that you purchased..
Of course you can get better efficiency and effectiveness if you purchase more licenses so that your staffs and cooperate and work together.
The pricing is designed to help all companies to get the maximum benefit with their investment.