7 Lessons From Entrepreneurs Who Kept Their Day Jobs While Starting Their Businesses The insight you gain while working for someone else can mean the difference between a successful entrepreneurial enterprise and one that fizzles.

Keeping your day job while starting a business has its advantages. Aside from the steady income and free coffee, reliable full-time work helps you flesh out your résumé and portfolio and extend your professional network. Even better, working for someone else gives you a front-row view of the best (and worst) ways to run a company, from managing time and money to handling customers and employees.

We asked some successful entrepreneurs who founded companies while holding down a 9-to-5 to share the lessons they learned.

1. First, prove your concept.