I currently work for a well known and highly reputable flight training institution giving dual instruction in a single pilot rated jet.
My students simply get right seat time, but all have COMM/ME/INST and around 300-400 hours. Even with that level of experience, they all still struggle with the transition.
Like the post above says, just because you can doesn't mean you should.
In your case, I damn sure wouldn't.
I've seen way to many of his type that think his money gives him some sort of above average ability to skip the basics and jump ahead.
Your a fool if you let him talk you into it. He will kill you.
All the best. Be safe.