hey can anyone give me any idea what could be wrong or is this is a normal thing

i got white smoke coming out when i start my truck its a 1990 mighty max but with in 5 to 10 mins its gone

i jsut bought it and got it cheap because of the smoke but did i make a great buy or break out even due to repairs

the truck has also been sitting for a while and i changed the oil/tranny fluid/ cap rotor wires and plugs/ and flushed the coolent