2001 Volkswagen Van smoke from exhaust

Hi there, I bought a VW Transporter yesterday and all seemed fine, I checked for smoke coming out the exhaust, funny sounds from the engine etc and all seemed perfectly fine. This morning I woke up and went to start the van after it had been sitting on the drive all night, quite abit of white smoke now comes out the exhaust and from underneath the drivers door for the first few minutes the engine runs. How serious is this and should the van be returned, I understand its an old vehicle with alot of miles but am worried this will become somthing more serious and the van wont pass its MOT and serivce in a years time.