Well if it is just salvaged because of water damage then there no real problem with the car. It's not like the car was in a crash where it could have really messed the frame and chassis up. So I would say your good on this one, although, I would still really look well for rust. You should really inspect the rear hatch, floors, under the battery tray, and the frame rails for any sign of rust. Any rust can be fixed though, its just a matter of how far you will go in caring for it. You might be able to knock off some bones on the car because it does have a salvaged title on it. Like I mentioned, as long as there is no physical damage to the chassis you should be home free, it'll be a little more difficult to sell though. Not sure how insurance works with salvaged titles. As far as the sunroof, I'm not sure I can help you on that one, but see if there is any rust around it. And if it does leak, a little weather stripping should solve that.
EDIT: If the water just went to the bottom of the doors, you might want to replace the carpets because mold and mildew linger deep in the fabric. Ask him if it was drivable after the flood too, that could help a lot.