BMW Repair: 92 325i, drain tubes, clogged drain

Question
I am looking to purchase a 92 325i 111,000 miles. needs a little work. the question i have is there is some rust in the roof around the sunroof. my first thought is it's a clogged drain, is this a common problem or is it a sign of serious damage.

Answer
It is most likely a clogged drain; though it's not too hard to test (cup of water).  the drain tubes can usualy be unclogged with some water and compressed air.  as for the rust, my main concern would be how bad it is, if it has seriously compromised the integrity of the metal you will eventually have problems with the sunroof operation.  On the other hand if it's not to bad you can put a rust inhibiting paint on it like POR-15.   It may be adviseable to take off the headliner to see where else rust has formed, if you can paint it before it eats all the way through the metal, you'll have less problems down the line.
-cheers