Forking out for a place to sit and eat is expensive enough, but you'll just be pouring money down the drain if you're planning on paying for a bartender and an open bar. Booze is expensive! Unless you don't mind turning your respectable shindig into a raucous kegger, it's best to buy some cheap liquor and pour the drinks yourself. Sangria, White Russians and limoncello are all easy to make with alcohol that's inexpensive and readily available. If a few bottles of vodka, Kahlua and wine are out of your price range, make the party BYOB. As long as you furnish enough for yourself and the happy couple, you should be OK.