Max, I looked into this as a meadmaker several years back. I've been brewing mead for about 20 years now, and wine and beer for about 8 years. Everyone who's sampled my brews really wants to be able to just buy it anytime they want. After much prodding I looked into it.
Your mileage may vary as I've kind of given up on these ventures because they are very cost prohibitive to get going. So take the advice for what it's worth.
First, you want to be a retailer; you must be licensed. This is VERY expensive and you have to purchase 100% of your product from a licensed Distributor. If your local distributor doesnt carry the beer you want to sell, you're SOL. You can request it, but Distributors need a LOT of demand to get new products on their list. Distributors arent monopolies by nature, usually most markets will have multiple distributors so you might be able to shop around, but smaller markets will be limited.
As a manufacturer, if you were to brew your product to sell it's easier but much much more expensive. When I priced everything out to just have required equipment it was over $200,000 and that was shopping around for used equipment (over $500 for all new equipment). But even then, you need to get special licensing to sell your product across state lines. Up until I think 2004 or 2005, all mail order sales required in-person orders (visiting a winery for example) This has thankfully changed but other issues still remain.
Many states will not allow alcohol to be shipped in under any circumstances. Some states have requirements on alcohol percentages.
Beer tends to ship one of 2 ways; either you're visiting the breweries website and ordering direct from the brewery Or beer of the month clubs. Again, even the BoM clubs tend to be one of 2 categories; either a single bottle of beer as a "sample" which is covered by different regulations and is easier to do. Or as a "middle man" type operation where the "club" is connected to multiple breweries that are already licensed to sell. At which point they just operate as order takers and have no licensing requirements to perform this service.
However, there's a few caveats. If a brewery went through the expense and hassle to get the shipping licenses; they dont need you. Those that havent been licensed for shipping either cant because of costs involved, or have been denied for whatever reasons (horror stories abound when it comes to BATF licensing and license maintenance).
With the budget you're talking, I'd have to say you'd need to double it just to get a lawyer involved so you dont suffer ATF raids or even jailtime for breaking rules.
Bottom line: you were successful because you completely bypassed city, county, state, and federal regulations. You were the only provider so you had zero competition. You are incredibly lucky that you got tapped on the shoulder by a brewer that said knock it off rather than face an ATF raid and prison sentence.
For $5k I doubt you'll get very far in the licensing business (most of them locally sell for $50,000 or more for retail licenses)