Anyone have any tips on what to look for to make sure a house is structurally sound?

Take a strong flashlight, a penknife, a 4 foot level, a tape measure, some string and a friend to hold the other end of it, wear old clothes, and tell the agent you will be there for quite a while and don't want to be rushed. First, stand way back, like across the street, and look at the house overall. Notice if it leans or sags anywhere. Then at the house itself, crawl around anywhere you can get to, under the house and into the attic if possible, and look for cracks, moisture, anything rotting. Sniff to see if you can smell any mildew or mould. Set the level anywhere you can think of to see if the house is consistently the same level or has dips and bumps in it. A whole house tilting all the same way is much better than one that tilts different ways in different places. Sometimes a whole block tilts toward or away from the road. Stand in each room and see if you see any inconsistencies in levels or is one room is at a different tilt than the next. Notice how the floor feels or sounds. Don't worry too much but consider if a room at one end appears to be tilted away from the house, because it may have once been a porch which had a sloped floor. Open cupboards. Stick the penknife in anything doubtful. If you can, it's rotten. Above all, take your time so you can receive impressions, as well as checking what you think you see with tape measure, level, and string. Doing all that should tell you if it's worth going on with a professional inspection