Someone asked if the architect shouldn't come first. Not necessarily. It depends on your lot size and shape, ...
Planning involves house plans, builder, building site, and mortgage. You want to be preapproved for a mortgage so you can grab that lot when you find it, BUT a mortgage depends on the house.
In my case, first we got a builder and got the architect through him. We worked with the builder and architect before we bought the land.
Stock plans can save you money, and you can change them.