In some regions, there is a second step you will need to take to insure your house plans are in compliance with local codes.
Some areas of North America have very strict engineering requirements.
In addition to the house plans you order, you may also need a site plan that shows where the house is going to be located on the property.
You might also need beams sized to accommodate roof loads specific to your region. You may also need a septic design unless your lot is served by a sanitary sewer system.
Examples of this would be, but not limited to, earthquake-prone areas of California and the Pacific Coast, hurricane risk areas of the Florida, Gulf & Carolina Coasts.