Ok, here's what I know - my limited knowledge of liquor stores:
I know some liquor store owners, including one guy that just got out of bankruptcy after losing his ass (and his store). Do your homework on the deal. Get the books, and give them the Abu Ghraib treatment - bring in the dogs, strip them naked, humiliate them - do what you need to do in order to get the right information. Make spreadsheets. Lots of spreadsheets. Get copies from the liquor distributor of the invoices going back a while and like Reagan said, trust but verify. Except without the 'trust'.
Does the area have a Wal-mart, and does it sell booze? Is there one planned? Wal-mart is pulling liquor store owners pants down these days - their prices are in many cases below the liquor store owners' COST.
Do some common sense thinking... For instance, one gentleman I know here has a hell of a deal going on - the City has an ordinance that says 'no sales after 9pm', and also 'no gas stations may sell alkie'.... his gas station is just outside the city limits, so he can sell until midnight - and he has basically cornered the market in beer sales to the 21-30 yr old crowd because those turkeys always run out of beer at 10pm and desperately need more for their after-bar parties and what have you. He's the only game in town, so he makes out like a bandit.
Food for thought.