That really depends on where you want the tap and where one needs to tap into the water supply. I fitted one myself yesterday, it took me about 1 hour and cost about �15.00 in total, I just needed to drill through the wall as my outside tap was being located literally on the other side of the wall to the cold water supply on the inside.
I would not recommend those DIY exterior tap kits, they keep clogging up and the feed is to small to get a good flow of water.