| find out what strings are on the bass. good strings cost 150-200 euros. so if the strings are crap and you have to buy good ones, it will add to the cost.
i would suggest to go to a violin builder with the bass and let it be checked, even at your cost. i would agree with the seller that if there are defects, he pays for the examination, if not, you. i'd rather pay 50 euros for that than paying expensive repairs later. repairs are expensive, i tell you!
600 euros isn't exactly much money for a DB.
in general, there is nothing wrong with old basses. | 
