Check for plumbing leaks as soon as you move in. Your home inspector should do this for you before closing, but it never hurts to double-check. I didn’t have any leaks to fix, but when checking my kitchen sink, I did discover the sink sprayer was broken. I replaced it for under $20.
Keep an eye out for dripping faucets and running toilets, and check your water heater for signs of a leak. Running toilets will empty your well real quick.
Here’s a neat trick: Check your water meter at the beginning and end of a two-hour window in which no water is being used in your house. If the reading is different, you have a leak.