Have a dealer run the VIN number for past service history.
The other thing I see is what codog mentioned which can be from roof or door leaks.
Car wash or high pressure wash may help show that.
2013 S4 Loaded (and NO RFT's) Awesome is an understatement
2008 MT X3
RIP you were a faithful sidekick and will be missed.
2007 AT X3 RIPOS
2000 Jeep Cherokee
1997 Twin Turbo RX-7
1984 GTI Wolfsburg Edition Neuspeed and more