actually, not so much. The improved (roads and utilities already constructed) cost about $80k for about a 6,000 sf lot. The water and sewer taps are another $ 10k (can be a lot more, depending on the location). Expect another $ 10k for surveying, plot plans, marketing, grading certificates, etc. You haven't paid for building permits yet and you're $100k down on a $ 400k house and you haven't even excavated the basement hole yet. Good luck making a 10% profit.