We are getting ready to purchase a 2004 home and it has a small crack ( less than 2mm ) in the brick on the outside of the home underneath the garage. The garage floor has small cracks, really hairline cracks. I have a structural engineer coming out to inspect, what should I be concerned withk?

It's a good idea to have an engineer look at this. Having said that, I would think that the small cracks you describe are due to normal settling of the structure. I'm having a hard time picturing the brick "underneath the garage" but a crack that small is not a serious problem over four years. A good clue is to look closely at the cracks in the floor. If the concrete is level across the cracks they are more than likely due to improperly mixed and/or finished concrete. If the concrete is not level, in other words, sections seem to have dropped or shifted then it is due to settling. I am a certified home inspector and would note this condition on an inspection report.

I agree and also have trouble picturing this bricks location. All concrete floor will have hairline cracks, that's why they scribe expansion lines in them. It just controls where the crack will be when it happens but it is of little concern. I would save the money of the engineers fee and just hire a regular home inspector. Far more things can go bad that a crack in a brick but a home this new should be OK if it was built properly.