A common place that Volkswagen Type 2 Camper vans can rot is in the bottom 2 corners of the windscreen panel. Its is easily temporarily covered with filler and a bit of paint. Beware this can get very expensive if it has been bodged up. Check these very carefully, take a magnet with you. A fully properley restored van would probably have had a new front panel fitted so this will not be an issue.
A bodged up van will have been filled. This will soon cause the paint the bubble and probably wont even last a few weeks. This will result in a proper repair doing. It will get very expensive as it is very labour intensive. A new Front Panel will cost anything from £60-£75.00 and a new windscreen seal would cost around £25 for a genuine vw one. Labour alone i estimate around £300.00 plus paint etc.
Avoid fully restored VW Camper vans that have not had a NEW Front panel fitted, unless you can see pictures of the van prior to restoration.