Writing a business model can be a very boring process to begin with but once you get those realizations of the time and money you could have saved yourself hadn't you done the research you will realize the value of doing your due diligence and why they say failing to plan is planning to fail! Fortunately for you there’s people like us around who can assist.
You really need to:
Know your product features and benefits
Know your market size, trends and customer profile
Know your numbers your capital employed (amount you invested and have working for you) and the amount you plan to make in return (ROI)
Many entrepreneurs like to finance their business as they go along, in the corporate business world we raise a budget, make a one time cash injection and monitor the cashflow. Pumping more money into the business to keep it afloat is a major sign your operations are not going well!
*find a management accountant , like i said there's people like us who can assist.