What all would have to be done to put a mobile home on a property?

The Properties is my father in laws and he already has a home on it however it is quite large and me and my husband are planning on moving it on here. since it already has a septic tank and water system is hooked up, what all would we need to do to be able to install the new trailer? would we have to pay for somebody to dig a new septic tank or would we be able to add pipes to the septic tank and water lines for our trailor? hope this is understandable ....i am just reqally lost on what all do we need to so.