With half a dozen states having launched recreational or medical sales last year, and an additional four states set to legalize medical cannabis this year or early next year, business opportunities are finally beginning to catch up with the wave of legalization.

That's according to the latest data from the Marijuana Business Daily, which has found there's generally a 18-24 month waiting period between legalization and the opening of the first licensed dispensaries/recreational storefronts.

In states like Delaware and Massachusetts, it took much longer - several years, in fact, between the legalization of medical cannabis and when sales started. Other states, including Minnesota and New York, moved much more quickly. Colorado, Oregon and Washington State averaged a wait of about 15 months after legalization before kicking off recreational retail sales.

With Alaska yet to sell legal, recreational cannabis despite having legalizing it back in 2014, columnist Becky Olson points out there are hurdles to be cleared in any new market, even after legalization.

"Marijuana businesses in each of the recreational states," writes Olson, 'have [...] met varying degrees of local government and community pushback, bans or moratoriums, creating ongoing challenges to establishing operations even in states with full legalization."

Check out the chart - or read Olson's full analysis here.