It’s not for nothing that I always say a business plan has to be your plan and nobody else’s. It can’t be your consultant’s plan. You must know it backwards and forwards and inside out, or it won’t work.

I learned this the hard way, sitting in venture capital offices at 300 Sand Hill Drive, the business plan consultant on the tail end of the new venture team. I had done the plan, built the financial model, written the text, shepherded the document through the painful coil binding and the whole thing, but I wasn’t part of the team. I didn’t want to be. I was still at grad school, getting my MBA, and my part of this venture was writing the plan, period. I needed the money to pay tuition.

In meeting after meeting, at key moments, the VCs would ask critical questions and all heads turned to me. I would answer.  I knew the plan, backwards, forwards, and inside out; but I was the only one who did. It was my plan.

It was a good founders team. It included three Silicon Valley veterans, a marketing guy, a technical guy, and a deal maker guy.  They had about 40 years of computer company experience between them. They had a good idea and, much more important, a market window, differentiation, and experience to make it happen.

The three of them never really got into the plan. It was a hurdle they paid me to jump for them. Every meeting generated new changes, so I would go back to the basement computer at the business school, and re-run the financial model. The team of three didn’t include a financial person to learn and manage the model, so it was always me, tweaking. Which meant I was the only one who knew the plan. I’d re-run my financial model, edit the text, and publish a new version of the plan. They read paragraphs here and there, glanced at the numbers, but they stayed with the strategy, and left the details to me.

Details that, in fact, they didn’t read. They trusted my faithful recording of their ideas, and my financial modeling. They assumed, I guessed at the time, that these were functions that could always be delegated to somebody with special skills, while they generated high-level strategy.

They did not get financed. I was disappointed. When you develop the plan and revise it dozens of times and support it and defend it through the long series of meetings with supposedly interested investors, you want it to take flight.

And time after time, when questions came, I was the only one with answers. It was my plan, not their plan.

All these years later, memory of that disappointment is still fresh. I did learn my lesson, though, and I changed my strategy as a business plan consultant. From then on I made sure that any plan I worked on belonged — and I’m talking about intellectual ownership here, conceptual ownership — to the real plan owners, not the consultant. And that made it my worst-ever business plan.

If you have the luxury of a budget to pay an outside expert, consultant, or business plan writer, then maybe you should use them. This might be a good use of division of labor, and perhaps you can lever off somebody else’s experience and expertise. However, that will not work for you unless you always remember that it has to be your plan, not the consultant’s plan. Know everything in it, backwards and forwards, and inside out.