After climbing to the No. 58 spot on the Inc. 500 list of America’s fastest-growing companies this year, Slingshot SEO’s team is often asked ‘How did you do it?’

With just $10,000 as our initial—and only—investment, our success definitely didn’t have anything to do with a surplus of funds. In fact, being forced to build our business on that meager amount played a huge role in our ability to become a leading search engine optimization agency–one that experienced 3,597 percent growth in just three years.

It was back in 2006, when I and a couple of my long-time friends, Aaron Aders and Jeremy Dearringer, launched Slingshot SEO with an extremely tight budget and a passion for Internet marketing. With our youthful exuberance came a willingness to make sacrifices; we took on some unprofitable projects to prove ourselves, we didn’t take a salary for the first year and we reinvested every penny right back into the company.

Looking back, it’s clear three major factors led to our exceptionally rapid growth in spite of our financial limitations, extremely limited staff and, basically, a zero-dollar marketing campaign. Those three factors were treating our customers right, focus and innovation.

From the start, we made a deal with our first customers that went something like this: “When we make you successful, will you agree to tell three other companies about your experience?” We knew the philosophy behind exponential growth—you tell three people, then you end up with nine, then 27 … and so on. And we always said “when, not if.” That’s how confident we were in achieving results. We targeted any decent company that deserved to be prominent on the web. With that strategy, Slingshot SEO managed to grow sales organically through word-of-mouth. We’re proof that this strategy works.

Another key to Slingshot SEO’s success was making the strategic decision to focus exclusively on being best-of-breed in one service. For us, that was clearly enterprise search engine optimization.

Like many Internet marketing agencies, Slingshot SEO started as a “jack-of-all-trades” agency providing just about everything to anyone. This lack of focus fostered mediocrity as we spread our talents thin over too many marketing verticals. We eventually agreed to focus on the area we’ve always excelled at—the acronym in our name, SEO. While ending engagements for other services was tough on business relationships and the pocketbook, it proved to be among the best decisions we’ve made to date.

Focusing on our core service allowed Slingshot SEO to flourish and innovate more rapidly than other companies in our space. The company’s limited resources were aimed at one offering. Today, Slingshot SEO remains one of the few agencies with an exclusive focus on enterprise SEO. For many, the allure of other services is just too great. For Slingshot SEO, focus is a competitive advantage. By focusing strictly on SEO, our teams are able to meet the varied and changing needs of enterprise clients as we manage their campaigns over time.

Another benefit of striving to make clients successful on a tight budget is that it forces innovation. When you’re a small Internet start-up, you’ve got to have a mindset of minimizing waste and uncovering the most efficient processes. You’ve literally got to maximize every dollar you have. From this desire to be nimble and adaptable, the company’s proprietary SEO workforce management software was born. This software platform enables us to track our workflow while being as efficient as possible in our operations.

So we started with just $10,000 and haven’t taken a penny of investment since; we’ve been able to build a business model that funds itself. As we prepare to celebrate the fifth anniversary of our business, it’s rewarding for us to think about how far we’ve come–and how we learned to be efficient out of necessity.

If you have dreams at building an Inc. 500 company on a bootstrap, believe that it can be done. You’ve just got to be flexible and focused, you’ve got to be innovative and you’ve got to treat your customers right.