Looking at a 2003 G35 with 67,500 miles for $4000 carfax came back clean taking for a test drive tonight any issues i shpuld be aware of looks very clean.
Google your make/model/year and look for any consumer complaints and reviews. AFAIK this is a fairly highly rated car so you should be alright. Ask for any maintenance records for the car, or where it was serviced at. This vehicle really does best when sticking with OEM (original equipment manufacturer) parts, hopefully the previous owner was servicing it at a dealership.