Is this a tricky question? If not, why not?

[Just a kid]

You're a CFI. A potential student comes to you. He has just bought a Lake Amphibian, he has no other ratings and wants to get his private SEL. Can you legally accept and instruct him?

 

[MauleSkinner]

As long as you have Airplane-Single engine privileges on your CFI certificate. The privileges on your pilot certificate will determine whether you have to fly exclusively off land or water.

fly safe!

David

 

[FlyingFisherman]

There's no requirement for your first rating to be ASEL.

I know a guy with around 1000 hours and zero single engine. Day one he started flying in his own Baron and to my knowledge never leaves the local area without an IFR flight plan.

That's the model owner-pilot right there for a Baron as far as I'm concerned. I'd love to be his insurance broker too!