For a typical private pilot 400-1000 hours. Not a test pilot. How many hours dual or checkout time to beat come proficient enough to be turned loose with it? Or are they difficult to master and need extensive training?
Sonex is a company that supplies plans and materials for amateur built/home-built experimental airplanes. They offer several versions of single and two seat light sport aircraft, and one small jet powered aircraft. A private pilot with 1000 hours should be able to fly one of their light-sport aircraft with little difficulty. The jet version may take some additional training.
Some transition training is advisable, how much depends on your skill level, but many average private pilots fly them. You will need decent tailwheel skills.