Now for the other side of the equation. The water you send down the drain has to go somewhere. If you're on public sewer, the city maintains those lines and takes it away from your home. A septic tank is just that. The water that goes down your drain goes to a tank that sends it into the ground to be absorbed. Some areas don't really allow for ground absorption, so those homeowners have to pay to have those septic tanks pumped out.
When you're buying a home and it has a well, or a septic system, you're going to want to have them tested. As you can see in the septic system picture, you definitely don't want the septic to contaminate the well. In the environment, there are all kinds of nasties that can get into the water. If the water gets contaminated, it can be treated. Even though this would be an extra inspection fee, you definitely want to make sure you can drink the water. Also the inspector should test the flow of the water in the home. You definitely want to make sure you'd have enough water pumping so a teenager could take their 1/2 hour shower, mom can run the dishwasher, and still have enough water coming in to flush toilets and have drinking water.
With your septic system, you need to have the lines checked, the tank checked, and the field inspected. The house my client is buying has a 15 year old septic tank. Even thought that may seem young, you would want an inspector to look at the whole system including the lines leading from the home to the tanks. The answer to the inspection should give you peace of mind. Either it's good for awhile, or it's good for now but you may need to replace either. So you would know that you may have that expense in the future.
Unfortunately wells and septic can be costly if they need to be treated, repaired or replaced. As a buyer, you definitely want to know that your water is potable, and what goes down your drains is going somewhere safe so as to not contaminate your water. AND, if you will have that expense in your future. It's money well spent.
If you have any questions about well and septic inspections, please feel free to give me a call. I'll be glad to refer you to an expert that can answer any question you may have.