What is the proper procedure when building a home at the bottom of a hill? Who is responsible for building a drainage so that there will no run off onto the property at the bottom of the hill? And should this be dealt with before the home is built?
This is more of a legal question and I'm not a lawyer.
My opinion only though there is some experience behind it.
The answer depends on several things. Who owns the hillside? They are the ones typically responsible to maintain it so it does not cause a problem for another's property. If that cannot be determined clearly, you would need to take whatever action you needed to protect your property from runoff damage such as swales and/or retaining walls ON YOUR OWN PROPERTY. If there is subsequent damage, your only resort is the legal tort system. eg a lawsuit.
If you are contemplating building on the site at the bottom of the hill, this is absolutely something that should be addressed before hand. You do not have the right to enter upon anyone else's property without permission. Typically, this type of engineering is done by a geologist or Geo-tech which is a combination of geologist and structural engineer.
I would consult with a lawyer that is familiar with this area of law.