If they don't, have the tests done anyway as a condition of your closing escrow. Parcels with numerous rock outcrops, swampy areas, water courses or ditches, and sparse trees and vegetation may be particularly suspect. A soils mantle test is usually one or more backhoe pits dug at least eight feet deep and observed by a civil engineer, geologist, or environmental health specialist. The soil can't have ground water or shallow bed rock. The soil should be reasonably able to absorb and filter water all the way down.
Percolation tests are a series of tests to measure how quickly the ground absorbs water.
They are usually run by one of the above professionals by measuring the drop of water in a post hole over time. Once your system is in, don't forget to maintain it by keeping the leachfield cleared of trees and brush, and by having the septic tank pumped when necessary. Okay, so utilities aren't a must with some people. Obtaining electricity, telephone, and other utilities requires that your land be reasonably near existing facilities and that there be appropriate easements allowing the utility company to extend their facilities. No one can really assure you about utilities, except the provider.