How much Alcohol/Drinks should we buy? Launch Party (for business)?

The rule of thumb is one drink per person, per hour. So if your party is to last 4 hours, you'd want to have 1,000 drinks on hand. Wow! Am I invited?

Unless you're getting kegs, one beer equals one drink. About six ounces equals one drink of wine. You'll have to do the math depending upon the size of bottles you're purchasing.

As far as the split between wine/beer/soda, you're just going to have to make some guesses. Is it more of a wine drinking crowd vs. beer drinking crowd?

As a place to start, perhaps you could do 40% wine, 40% beer & 20% sodas.

One rule of thumb is to allow 2-3 drinks per person per hour. Your best bet is to explain to your liquor store (or supermarket or whatever) that you're buying more than you might need and make an arrangement with them to take back any unopened beverages. Most places will work with you on that. I don't know if you're planning to serve any finger food as well, but a large supermarket like Safeway can provide the snacks and that makes arranging a take-back of beverages even easier.

Good luck with the business!

Find a function room in or near Chicago, if it's in your budget. Don't serve your own liquor. Let me advise you here, Don't serve your own liquor. Unless you have a food service license, you can't serve ANYthing that isn't pre-packaged. Let the caterer or hotel do all that for you. It's probably in their contract anyway. You will discover that it's going to be an expensive opening. I hope it's in your budget.