if is etm is that a expensive job? anyway to tell,

So i need to get on a code reader on it

Hi, I picked up a 2001 140 v70 today for a bargain price its in mint condition but its got a problem as i have never owned a volvo before im unsure what it is When its warmed up it has a rough idle and hunts between 500 - 1000 i knew this when i bought it but took the risk , I drove it home 45miles ...