Just a couple of quick notes on a Perk Test
After finding the property, you should have a perk test done to determine the soil and suitabilty of the land for a sucessfull leach line.
You do want to contact a qualified contractor to determine where the perk should be done at this is determined by the way the home will sit on the land.
Next contact a licensed engineer that can perform the perk. Note depending on the land size there are different perks to be done. Check with the building deptartment to determine what the specs are.
If you fail the test don't worry just tell them to make cottage cheese out of the land and find a place were it will perk. Then go back to contractor and planning a different site to build on.