If you dream of building a custom home on your land, the land itself can be a make-or-break item. It's the biggest single-item piece of your budget. You will invest anywhere from 15 to 50 percent of your overall custom home budget on your land, assuming you can even build on it. When buying rural land or undeveloped land in particular, there are some deal-killing pitfalls to avoid. The same is true even for buying a developed lot in some cases.