Finding an architect to design the home is step two. Then you can competitively bid out the design among several builders.

I would assume some builders prefer to use in house architects.

You can obtain plans in several ways. You can have an architect, plan designer (draftsperson) or a design/build contractor help you create custom plans. You can also purchase plans on various websites that are 'off the shelf'. You can talk with these various sources to see what is right for you. Be careful that you understand EXACTLY how each works and who owns the plans and rights to build from the plans when the process is done. It appears that many people get a rude surprise to find they don't own the plans at the end of the process.

What we have started to see in our area is consumers going to architects and/or plan designers and having broad brush, concept plans done (which I assume costs much less) and then they go out and try to get bids. There is not enough information and detail on the plans for a contractor to actually give an estimate much less a bid. The plans certainly could not be submitted for permit application/plan review. More likely than not, the consumer is shocked at the prices they get back for the project.

Good luck.