A home inspector should check plumbing for leaks, corrosion, water stains, proper trap installation, secure fittings, functional shut-off valves, signs of mold, appropriate pipe materials, and ensure drains are clear, vented correctly, and sloped properly for drainage.

A trombone comes to mind... Or maybe miniature golf.

Drainpipes under a sink should be simple: a small U-shaped bend called a “trap” holds a plug of water to prevent sewer gas from rising out of the drain. This plug of water should never be more than 4” deep and the remaining drainpipes should be as short and direct as possible. The drain plumbing under this sink contains three traps (one’s upside down), and holds far more than 4” of water. It’ll tend to have problems draining and will clog easily.