Given the typical good health of undergrads, you might wonder: Why are so many companies eager to open medical marijuana dispensaries near the University of Massachusetts?

The latest count is four, with another proposed just over the line in Hadley. If blood pressure is running high, it’s likely because entrepreneurs are stalking a big score.

Businesses are betting public opinion polls are right and that passage of a November ballot question will usher in a new age of weed. Dispensaries would convert to retail outlets on the double – and that’s why they are being proposed.

Fall will bring a high-stakes campaign for and against legalization, one that replays Colorado’s debate in 2012, when residents backed recreational marijuana, 55-45. Today, Boulder, home to the University of Colorado, has issued at least 81 licenses to grow marijuana, make products with it and sell at retail.

There’s money to be made — and a lot of it. A survey this year by ArcView Market Research estimated that if the ballot measure in the Bay State passes and retail sales begin in January 2018, the legal marijuana trade in Massachusetts could be worth $1.1 billion annually within four years. A recent gathering at Microsoft’s NERD center in Cambridge saw venture capitalists mingling with entrepreneurs in search of the right opportunities.

And for as long as it stands alone among East Coast states to allow use of recreational marijuana by those over 21, Massachusetts would attract “canna-tourism.” The prospect of a big new market is bringing out the big guns.

In Amherst, there’s a veritable land rush. The Select Board in June provided a letter of support to a fourth proposed dispensary. This latest entrant has offered to pay $2 million for the Amity Street home of Rafters Sports Bar & Restaurant, more than twice its assessed value, putting it out of the reach of Rafters’ owners, who hold a right of first refusal.

Before voting 4-0 June 20 to issue a letter in support of Happy Valley Ventures MA Inc. of Newton, Amherst officials did pause to discuss whether they are paving the way for University Drive to become a pot highway.

Not necessarily. The proposed dispensaries must win OKs from the Zoning Board of Appeals and the state. One of them, Mass Alternative Care, already has both for a dispensary at 55 University Drive. The ZBA will continue a hearing about a proposed 169 Meadow St. dispensary July 21.

Planners assure the public that all are getting close looks. But the ground rules have been changing. When Amherst shaped zoning rules for medical marijuana dispensaries, the state had capped the number allowed at five per county. But that limit was tossed out by Gov. Charlie Baker’s administration, leaving towns like Amherst scant time to devise new rules, Select Board member Douglas Slaughter noted last month. “It puts us in a bit of a pickle,” he said. If recreational marijuana use becomes legal, dispensaries in Amherst would need to obtain new special permits, perhaps lessening the tang of that pickle.

Baker and Boston Mayor Martin J. Walsh will now help lead the charge against legalization through the Campaign for a Safe and Healthy Massachusetts. They’ll argue that legalization is bad for young people, just as Colorado Gov. John Hickenlooper did, unsuccessfully, because it will increase their access to the drug. They’ll note that Colorado now has the nation’s highest rate of youth marijuana use.

In Colorado, proponents of legalization made an argument similar to casino legalization in Massachusetts, arguing that people are going to use marijuana (or gamble) one way or another, and it’s better for the state to benefit from tax revenues.

Meantime, people who try to help young people avoid risky behaviors should get marijuana on their agendas. Two members of the Amherst Select Board who serve on the Campus and Community Coalition to Reduce High-Risk Drinking say that group hasn’t decided whether to list marijuana as a substance of concern.

We’re not sure what they’re waiting for.