It depends on where the sewer main is exactly - if it is well away from the house or on the street then you should be ok. If it is close to where you want to build then you really need to check its depth and consult an engineer to make sure the house footprint and foundations are far enough back.
The easiest way is to go to the Dial Before You Dig website and lodge an enquiry with your address. Then have a look at your water provider plans to see where it sits on the site. Here in the Central Coast, the Central Coast Council manages water and sewer so you need to check their plans for the sewer location. If you were in Sydney it would be Sydney water to check., if you were in Newcastle it would be Hunter Water plans to check for sewer location.
A sewer peg out sets out the exact location and depth (invert) level of the sewer so that your engineer can design it according to the council guidelines which can be found here.
A long section will show you the invert levels for a sewer - it is not as accurate as a sewer peg out, it is good to have at the feasibility stage though so that you can ask your engineer how far away the footings and building footprint need to be. It costs $42.18 from council, there are directions on how to apply for it below.