Some experimental aircraft are available only as plans, and no manufacturer makes a kit for them. If you select one of these plans you'll wind up gathering all the parts yourself from various suppliers that serve the experimental aircraft hobby.
Plans can be as simple as low-cost reprints of aircraft plans that have been around 50 years or more. Or the plans can include full-size templates for major components that you trace on to the material before cutting it out. The cost of such plans range from free to $1,000. You typically get what you pay for.
Those designers who provide plans and drawings for a price usually offer an information pack that you may buy to help you decide whether to purchase the full plan set. These information packs run about $20 to $50 depending on whether a video or other helpful resources are included. You will find plans sources in magazines such as Kit Planes. Once you’ve narrowed your interest to one or two plans you can buy an information pack to help in the final decision.