How far of a distance from the house are they located

By code they should be within eighteen inches of the house. However, there are many homes that don't even have any at all. Or if the sewer has been dug up, they put them in a convenient location. Pretty hit or miss, unless the house if fairly new.

If they exist they can be 18" inside or outside the home right on the main drain. Tell us more about the home such as location, age type of pipe.