I did mine in 5 days. No prior jet experience. They expect you to studdy before showing up. You must be proficient at flying by instruments and multi. They do a sim (AST hawk) check for your instrument skills before you even look at the jet. The ground school is the hardest part. They make notes for you and hopefully you learn it all. The flying is easy, well easier than a piston twin. Very stable and don't have to worry about props, mixture, cowl flaps, etc. At this school I went to, most of their customers have signifcant flight experience, I showed up w/ 380 TT and 65 Multi. They were going to turn me away, but I wanted to do the VA approved course which has 7.5 hours of flight. One of the guys in my class had gone through Flightsafety for a different type rating. Their course was about 12 days, I asked him the difference and he said that they spoon feed the information compared to the place we were at. They also dont expect as much self study before showing up. This place had an examiner on staff, but he wasn't easy. ATP standards to the letter. Drop below GS on an approach and the checkride is over. If it can be done in 5 days, I'm sure it could be done in 4. However, my experience with ATP's is that they train you for what their examiner will ask, but those A** H***s didn't put me with their examiner, and I looked like an idot on my checkride. Passed anyways though.