Assuming ownership of a longtime college hangout sounds like a tricky proposition, especially if you鈥檙e just barely out of college yourself. Yet Mark Heinritz, his brothers Chris and Jim, and their friend Cameron Stainton鈥攁ll in their mid-20s in 1992鈥攆elt up to the challenge of running The Sink, the venerable University Hill institution just steps from the CU campus.