Summarize the following:
You can call your state to check the zoning laws of your property to see if you are  allowed to put a new building on your property. You don’t want the state to ruin the fun by fining you for your newly created underground house. Even if you’re underground you're not safe from the law. More official business. You need to pre-mark  the area on your property that you want to excavate with stakes and white paint. Then you call your state’s Dig Safe branch and describe the area that you plan to dig in. Hopefully they will grant you permission. You definitely have to do this to ensure that you’re not going to dig into a sewage system or something like that. Hiring a professional to do it for you wouldn’t be the worst idea. Depending on the size of your house you probably are going to need to use heavy machinery, and if you have no experience with that hiring a professional is probably the way to go. Search for professional excavators on the internet or contact a local construction company. They should be able to quote you a cost and at the very least offer you some helpful tips. You may be able to negotiate a price to use their equipment if you can prove that you are trained to use it. This isn’t a solo job even if you really want it to be. When you’re excavating or dealing with heavy materials you need someone to make sure that you are safe. You are going to be dealing with a lot of heavy materials and working in the earth and something could happen at any time. Make sure you have a partner. Look for a spot that is outside of your area’s 100-year flood plain and isn't near any steep slopes that might trigger a landslide. A large open space is probably best suited for an underground house, because tree roots can also cause issues during excavation. The odds are that you will be trying to build this house on your own property, so you probably don't have to worry too much but just be aware.  Generally you want to stay away from any large objects like trees, boulders, or multi-story buildings. You also shouldn't place your house near any concentrations of fuel or any hazardous materials.

Summary:
Check your zoning laws. Get permission from the state to dig. Hire a professional excavator or buy professional equipment. Find someone willing to help you. Find a suitable location.