Oil Leak on 2005 Volvo S60

I am looking into buying a 2005 s60 and the owner reported it needing a quart of oil in between oil changes. Is this common and does anyone know what may be the problem? It is not a turbo and the current owner does not report any visible leakage.

Asked by for the 2005 Volvo S60
How many miles are between oil changes?