If you want to build a special home for your family which is specifically designed keeping your family in mind, then you need to hire a custom home builder. Normally, an architect would be creating the plans for the home and the builder would work on the construction to help build the dream home for the client. The client would decide the layout and features of the home.
Typically, the client would already have the land for the construction of the home and the builder would construct on that land. However, there are cases where the builder would sell land specifically suited for the construction of custom homes. In such cases, the construction would be a lot easier. But, flexibility is the key feature of going for a custom home instead of a regular spec home.
Custom home builders never use stock plans. They would work on plans specially designed keeping the interests of the client in mind. Different kinds of custom homes can be built. Construction of a custom home would usually handled by a competent builder such as Merlin Custom Home Builders in Las Vegas.