In most states I'm aware of, you'll need an approved septic design and inspection during construction. There are many designs, but they basically consist of a septic tank for solids and leach field to evaporate water. The size of the tank is generally based on the number of bedrooms in a house, as is the size of the field. Soil conditions can affect the field size as well, and percolation tests are done to determine how fast water will move through the soil.
Unless you have a very high water table, you should not have much trouble putting in a proper design. On bad soils, sometimes it is possible to build an area up with fill, and use that for the field.
You mention a well too. The kind of well you need depends on a lot of things. In consolidated aquifers, artesian wells are most common. These are drilled to bedrock until they intercept an adequate seem of water. In un-consilidated aquifers you can have driven or dug wells. There are guidelines for how close a well can be to a leach field of course.