For contracts about real estate, the notary public is obligatory.
The Civil Code has a large chapter about the sale contract.
There is a responsability of the manufacturer of goods.
There is a special legislation about the sale of real estate which has to be build after the sale.
This page in Dutch
This page only contains some general information, which can help you to understand law. For complicated legal advice it's best to have a lawyer who knows what you need.