Other things that came to mind:
Check the appliances for age/wear, and find out if they're taking any with them. Maybe not an issue since you said this is a flipped house but if it has old appliances check them.
If the house has a septic system have that checked, you don't want to have to dig that up for repairs a year after you move in.
Run the hot water and see how long it takes to get hot, and also your water pressure. Run the shower and give the toilet a flush at the same time.
If the house has a basement check it for signs of a homo dungeon.