First and foremost, hire a good septic designer to do the necessary tests and drainfield design, BEFORE you design the house!!! Go out with them and tell them where you would like to situate the house, but let them give their input. Sometimes just moving the house a few feet in one direction will make the difference between a regular, gravity fed system and a more expensive pump system.

I had some friends that were going to build and I tried advising them on this, but wouldn