You can either hire an expert BP writer or buy an off the shelf package.
I personally don't use them as such (a detailed 12/24/36 month P&L Spreadsheet is good enough for my own satisfaction) but then again I personally have never or agree with borrowing money

BP can say whatever you want them to say so I rarely see the point in them. However I appreciate banks and investors require them.
Alternatively there are free samples on the net to download which will give you an idea if you want to do it yourself.
Depending how much you want to borrow should dictate on how much you spend.