Putting on my MBA hat that I don't get to use much in FIRE, pardon the rustiness...
It sounds like an interesting idea that may have potential, but ideas are a dime a dozen. And, as others here have implied, basing success on assumed on-going government protection is risky. There's no guarantee that liquor stores will maintain a monopoly on certain beverages or the 3000' distancing. Any whiff of change in the air and it's already too late, the value of the business drops overnight.
More importantly, you've outlined a *very* preliminary idea that's impossible to evaluate with a lot more detail. Detail that you need to flesh out as part of your due diligence.
Let's get one thing out up front: Liquor stores are a commodity retail business, margins are razor thin.
Start by doing a detailed Break Even Analysis (search online for resources about this): What are the fixed costs, variable costs, and average price per unit sold. This is a framework for organizing all the data you can get your hands on: taxes, licensing fees, payroll (incl. taxes), insurance, legal fees, accounting fees, COGS, advertising, initial build, and so on. How many units do you have to sell to break even (e.g. cover your costs). Important: YOUR pay should be included in this analysis. Don't make the mistake of thinking you can go without a paycheck to help get the business bootstrapped. This is the fast track to burnout and wrecking your personal finances.
Next, you need to do market analysis. This is a lot more subjective than the break even analysis. People tend to be attached to their idea in this analysis, and so they see what they want to see to support their bias. Don't do this! Guard against diluting yourself as this will only hurt you down the road. You want a brutally honest assessment of the viability of the business, not a rah-rah pep talk divorced from reality. With that said, what is the market for liquor store products in this location? Realistically, how much of the market would navigate to this location vs. existing retailers. I'm talking customer base right now, not in the future. If the customers aren't already there you won't last past the first year... you will build out a store, struggle, go out of business, and then the next guy will come along and buy your business for pennies on the dollar and then be successful because by then the customer base is there.
If you have ample demand to push you pass your break even point then it's probably a good business. If not, it's a hard stop. No excuses, no justifications, no magical thinking. Just no.
Even if you get to this point, there are other wildcards you need consider, things like how long (and how much does it cost) to get a license. And what is the permitting process like. And will neighbors be able to block your permit application (many folks don't like having liquor stores in/near their residential neighborhoods). And so on. Write these down, try to put numbers/estimates/probabilities around these.
At the end of the day, business is brutal and unforgiving. It's entirely up to you to do your homework and do everything you can to improve the odds. Most businesses don't survive 5 years, and many that do "survive" are killing their owner(s) behind the scene. It's far better for a business to fail on paper before you dump a lot of money into it. But if you do find a business that pencils out it can be very rewarding... still difficult, yet rewarding.
