A lot if builders. Or you can buy plans from someone who does. You can get a plan from a book. If you build your own house and have a structural engineet stamp ityou can do what you want. If the builder provides the plans, they are doing it as part of the service they provide, which is to build a residence. They aren’t selling a plan, they are selling a makee. In a title state you cannot call yourself an architect but you can provide the equivalent service if someone else is stamping your plans. California is a title state. In a practice state, you cannot provide the service unless you are licensed. This is regulated state by state.