Which is a very important part to prepare a Business Model / Plan? a. Cash Flow b. Profit & Loss A/C c. Balance Sheet d. Investment Schedule e. Others?

Cash Flow - eventually cash flow represent all the parts of good Business model/plan.

all of those

investment schedule , profit& loss , Balance sheet, cash flow , forecasting m marketing studies , determine Target suppliers and target customer , define your strategist  (study all project side very well )