Sandal-clad hippies in tie-dye shirts. Stoners so high they can barely put a sentence together. Foreign drug runners, gun-toting gangsters, and hardcore criminals.

These are the images many outsiders have of the medical marijuana industry.

I should know: Many of my former colleagues, friends, and family members mentioned these stereotypes in 2011 when I accepted a job helping launch a new publication covering the business aspects of this emerging sector. In all honesty, I shared some of these concerns as well. As a long-time business journalist in the mainstream media, my professional and personal reputation was on the line. Moving from a daily metro newspaper to a “pot” publication caused some head-scratching among many acquaintances – even though I was entering a $1 billion-plus industry at the time.

To be sure, I certainly did run into some people who fit this description in the early days of our publication. And I still do now.

But here’s what is most surprising to many about the marijuana industry: It’s filled with straight-laced people who built careers – and started successful companies – in other fields. And more are joining every day.

Professionals from the banking, finance, investing, and accounting worlds. Interior design specialists, journalists, and healthcare veterans. Technology, marketing, retail, HVAC, construction, and manufacturing pros. The list goes on.

In the past few weeks, a cannabis-focused private equity firm hired a former DEA agent and a publicly traded marijuana company brought on a former executive at Yahoo and Microsoft as its president. A former Congressman is also bidding for three dispensary business licenses in Massachusetts.

The reason for the mainstream interest is simple: This is a legitimate business with many attractive opportunities, and it’s now one of the fastest-growing industries in the country.

U.S. medical marijuana sales hit an estimated $1.5 billion in 2013 – up about 15% from the year before, according to our 2013 Marijuana Business Factbook.

Impressive, but that’s only the start. Overall marijuana sales in states where cannabis is legal could double in 2014 to hit $3 billion, according to our estimates, as Colorado and Washington begin selling cannabis to adults 21 and over.

Earlier this year, we projected that sales will hit $6 billion by 2018. However, the outlook has improved drastically since then (in large part because the federal government said it will take a hands-off approach to states that legalize marijuana for adults). Marijuana legalization could spread like wildfire, and industry sales might therefore end up being much higher.

What’s more, these figures are just for marijuana transactions. Hundreds of millions of additional dollars are being spent on professional services, ancillary products and other offerings. Like any industry, the medical cannabis sector needs everything from lawyers and accountants to human resources professionals, insurance specialists, and consultants. There are hundreds of other companies making packaging, equipment to extract cannabis oils from the plant, inventory software, you name it.

Here are some other reasons why many are bullish on the industry’s potential:

Efforts are underway in a handful of other states – including heavyweight California – to legalize marijuana for general adult use, while several others (such as New York) are pursuing medical marijuana legalization. The dominoes are falling. Currently, 21 states and the District of Columbia have passed laws allowing the use of medical cannabis. In the coming years, more than half the country will have legalized medical or recreational marijuana.

Poll after poll shows that the overwhelming majority of Americans feel that medical marijuana should be legal. Earlier this fall, a Gallup survey found that 58% also support the legalization of cannabis for adult use – the first time a clear majority of the population has favored legal marijuana. In 1969, when Gallup first asked the question, just 12% of respondents backed the idea.

Companies are beginning to expand beyond their home markets and into other states. The founders of California-based Harborside Health Center – the most successful dispensary in the US with sales of more than $20 million – are hoping to branch out into new states as soon as possible. Dixie Elixirs, which makes marijuana-infused sodas, ice cream, and other products, and dozens of other businesses are expanding nationally as well.

This could become an international industry in the near future, boosting business opportunities for U.S. firms. Uruguay recently became the first country to legalize marijuana possession, use and sales, while Canada has opened up its medical cannabis business to the free market. Other countries also are weighing marijuana legalization or relaxing cannabis laws.

That’s not to say everything is rosy.

Don’t forget: Marijuana is still illegal at the federal level. The risks in the business are huge. Executives could face criminal prosecution, and investors could lose everything overnight if the federal government or local officials crack down. That’s why average interest rates on loans to medical marijuana businesses hover between 20% and 30%.

Banking and payment processing are significant issues, and many businesses that handle marijuana directly have to operate as all-cash businesses.

Additionally, marijuana is one of the most volatile industries in the corporate world. State and local regulations change constantly. Cities can enact bans on MMJ businesses without much warning. And the costs of doing business in a heavily regulated industry can be prohibitive.

But the potential is so immense that many are flocking to cannabis. One day, I have no doubt we will see household brands develop. There will be retail marijuana chain stores a la Starbucks and cannabis-infused beverage brands like Coke. Major players in other industries – possibly Big Pharma and Big Tobacco – will most certainly enter the industry down the road. Marijuana companies will trade on the major stock exchanges, and they’ll have global businesses.

Soon enough, the industry will grow up and get buttoned-down. But for the professionals who can stomach the risks, the time to get in is now. They’ll get in on the ground floor of a brand new industry, and help determine its shape . You don’t have to be smoking something to see that as the chance of a lifetime.