2007/2008 Volvo S40 or Audi A4?

So I'm looking to buy a new car ASAP but I'm stuck! I'm really interested in a 2007 or 2008 Volvo S40 or Audi A4 but I'm just concerned that the parts might be too expensive if something goes wrong? Are these cars reliable? I was looking into VW Jetta as well but have heard mixed reviews. I'm trying to do some research online but I need helppp!!!!