Understanding how critical sales are to a new company, startup founders often are eager to put cadres of professional salespeople to work for them. But not so fast, experts say.

"There's a pervasive myth in entrepreneurship…it's the myth that you need professional salespeople right off the bat," said Craig Wortmann, a clinical professor of entrepreneurship at the Chicago Booth School of Business.

Early in the life of a business, it's most important that the founder sell the company's product rather than a hired salesperson. Here's why:

The founder brings a passion for the product or service as only the founder can. He or she can communicate personal stories that will captivate those first customers. In the early days, you have myriad reasons you decided to bring your product to life. These are powerful assets to an early-stage company. As your company matures, you can build sales on the experiences of customers and how they've engaged with and used your product.

Related: 4 Selling Essentials Every Startup Should Know

Selling in a startup is different from selling in a big company. In the early stages of a company, you're not only building the sales story and process, you're also evaluating whether you found the right customers for your product. You're still working toward the right product, and as startup guru Steve Blank put it, you're still searching for a scalable and repeatable business model. Insights from your customers can be invaluable to this process, Blank and others advise.

Selling your own product sets the tone for your employees. If you are able to sell the product to customers, you can sell it to those who work for you. Early sales can generate important stories that you can share with future salespeople and employees that can motivate them to pour passion and energy into helping you succeed. Stonyfield Farm conveys its mission through references to the early days, when co-founders Samuel Kaymen and Gary Hirshberg "did most of the work" -- "They milked the cows, made the yogurt and made sales calls and even deliveries."

Related: The 7 New Business Facts Of Life For Entrepreneurs

Hiring and training salespeople can be a costly proposition. In the early days of a startup, it is wise to marshal resources and evaluate carefully where to spend scarce time and money. The late Ewing Marion Kauffman, who grew his pharmaceutical company, Marion Laboratories, into a multi-billion dollar enterprise, did his own sales when he first started his company. He hired salesmen only as he could afford them and invested a great deal of time and money in training them.

In the early stages of the company, the founder may find him or herself performing any number of important tasks. Along with vision and strategic planning, founders might also be building furniture, installing whiteboards and refilling the coffee pot. In between all of these jobs, founders must secure customers for the fledgling business. And even for people who consider themselves sales "naturals," sales can seem daunting.

Selling can help you develop resilience in the face of rejection, handle objections, master the art of conversation and develop the best possible sales model for your product and company. Put yourself to work in sales for your company: Be the sales you want to see. 

Related: Richard Branson on Turning an Idea Into a Business