If i build my own house, septic permits? building permits?

Your land is in some type of municipal district, whether it's a town, city, county, etc. That governing authority will have the requirements for construction in the area. Find out who the official is that oversees that department and make an appointment to talk with the chief inspector. They will tell you what permits you need to legally construct a dwelling. And, yes, they can make you tear it down but that rarely happens. What would probably happen is they'd make you open up all the walls so they can see the plumbing, wiring, etc. Expensive. So, do yourself a favor and contact the proper authorities.