Before putting your house on the market, attend a few open houses at similar properties in your area. That will give you a firsthand basis for comparing your home with competing properties. It's also a good way to take the pulse of the local market and to spot some of the selling brokers who are active in it.
Although most water heaters last 10-15 years, it’s best to start shopping for a new one if yours is more than 7 years old. Doing some research before your heater fails will enable you to select one that most appropriately meets your needs.