YES, entirely common, and frankly DON'T BUY IT.  I looked at a very
nice 4wd '87 for $3500 with a fresh rebuilt tranny and strong engine,
looked good outside then I looked under.  I've learned from my '85.
First all VW cadmium coated parts rust swiftly and terribly, it is
obvious VW did no long term testing in salt laden areas.  The cad
coating sets up electrolysis and I swear the parts go faster than if
bare steel.  Cad coated stuff includes most all A/C & P/S lines, most
hardware (nuts bolts locks etc).  Brake lines likely gone as well
especially the unions.  Frankly people it just isn't worth the effort
no matter how good a deal you were to get and the asking price of the
van in question should command incredible condition top and bottom.
Another neat one, Engine and Tranny case, particularly that pricey 5
spd, may be severely corroded, head bolts, aluminum leached out
tranny and engine case under steel through bolts, on and on and on.
In general, never buy anything for anywhere near retail if it has
been run year round in the salt belt, you will HATE yourself later.
Particularly as the car gets to be over 5 years old.

John
vwbus@netbiz.net