It depends what you want. Want water? ... need faucet, plumbing, and fresh water tank plus pump. Want toilet? .... need plumbing plus blackwater tank. Want heat?... need furnace. Want hot water? ... need water heater. Don't forget propane tank and plumbing. Want refrigerator?.... need 2 or 3 way refrig. Want storage? ... need cabinetry. Want fancy electrics? .... hold on to your wallet! You can get $500 dollared to death building your van on items like these. If you get a used rig, odds are you need a few repairs and upgrades. Do not discount the value of a factory built rig with all the comforts of home.