Is it ok that the drain line for a septic system is above ground?
It would seem strange that the waste drain pipe goes straight out of the house above ground to the mound.  The primary purpose of the mound is for the distribution of water after it has passed through an enclosed septic tank and a pumping tank.  These two chambers are normally underground.  The pipes from the pumping stations would also be underground up to the mound and still would be buried in the mound as it travels to the top of the mound to the water distribution pipes.
I would have the owner explain where the septic tank and pump tanks are located and why the pipes you see are above ground.
Photos and more details on the pipes would be helpful.  Are these pipes on the surface of the ground?  What is the distance from house to mound? 
Is it OK, depends on whether a fully functional septic system has been installed.