In order to have a  functional wet bar or even a full kitchenette you need to take care of plumbing. There are 3 steps to handling plumbing for a new wet bar. #1. Rough-In, #2 Sink and Faucet Installation, #3 Dishwasher and other appliances. The first step is so called starting job, which is done at the time your basement is being renovated. Second and third steps are finishing jobs, they are done once the bar is already installed. While it is possible to do a rough-in on an already finished basement. Costs can be significantly higher due to the complexity of work.