this really is a non issue IF you maintain the car correctly...

the old red block engines (B230 etc) as found in mos earlier volvo's (240,740,940) were (alledgedly) non interference, the six cylinder engiens always were interference (260, 760, 960 - if we ignore turbo engines).

MOST cars for the last 30 or so years have had interference engines (interestingly some hondas dont..) and PROVIDED you change timing belts on (or before!) time you will never know the diference...

IF you negelect a timing belt (or get VERY unlucky) and it snaps on an interfecrence engine it will certainly damage valves, probably pistons, perhaps con rods & crank, perhaps cam shafts...

however if you maintain your car correctly you SHOULD not have the issue...(unless VERY unlucky)

Basically I wouldnt buy it unless their is either a clear service record stating its been done, or the seller is willing to get it done - and you TRUST them to do the job. Personally whenever I have bought cars I ALWAYS get teh belt done anyway for piece of mind (even on red block engines which CAN be interference IF you get REALLY unlucky alledgedly)