I think I reached my 40s with 20 years in real business and an MBA degree before I ever heard the term “business model.” It became fashionable in the late 1990s when Internet companies were absorbing millions of investment dollars on businesses that had no way to make money.
The business model became the buzzword that explained how a company makes money. One of the more amusing points about “business model” is how its definitions are so vague and far ranging. For fun, you can go to www.google.com and type “define: business model” into the searcher. You´ll come up with about a dozen definitions ranging from confusing to extremely vague. My favorite (from www.changewave.com) says “In the New Economy it means: What does a company do? How does a company uniquely do it? In what way (ways) does the company get paid for doing it? How much gross margin does the company earn per average unit sale?”
I recommend that you avoid the term business model in a business plan. Instead, cover the bases that all business plans cover, produce your financial projections, explain point by point your company, what it sells, its market, its strategy, its management team, and its financial projections. Let the business model explain itself. From what I see these days, people who talk about their business model usually don´t have one.