Your hot water heater just exploded. You have 72 hours to find a replacement before out-of-state family arrives for the holidays. It's not time to panic; it's time to get connected.
Start by posting wanted ads on free, classified ads sites such as Craigslist. Call your friends and family and let them know that you need a water heater, pronto. With any luck, they might have a friend who's looking to offload that product for cheap. The people you know best are your primary resource for locating quality used appliances.
But don't wait on your friends. Search the classified ads on Craigslist, your local newspaper and eBay, too. Call local appliance and hardware stores to see if they're running any specials or have gently used or slightly damaged products for sale.
If possible, arrange to see several similar products in a short amount of time. That way, you can compare them by price and by condition. Ask to see them plugged in and working. If a seller balks at that request, move on. Press buttons and play with the knobs to make sure they're functional.
Listen for weird sounds or other telltale signs that an appliance is on its last legs. Look for signs of abuse or neglect; if you're buying from private sellers, observe the condition of their home. This can tell you a lot about how they treat their belongings.
If it's a truly major purchase and you aren't sure about an item, you can always call a professional repair person to accompany you and perform an inspection. This will cost you some cash, but a pro can almost always identify major problems.