KSU Aviator is wrong...
I have over 1,000 hours in the BE-99, all of it during 135 ops and all of it alone. We had no auto pilot.
We also flew the BE-1900 single pilot with no auto pilot, but that of course required a single pilot type ride. Busy, but fun.
The old C model 99 was a great airplane, the A and B model left a little to be desired... and you are right, since it was under 12,500 lbs it did not require a type ride - just a regular old 135 IFR check ride.
You can put a guy in the right seat, but you sure don't need him. When I left the freight industry and started flying the BE-1900 for an airline (street captain), I remember being somewhat bored because I had someone sitting next to me doing most of the work!
Enjoy the 99!
I definantly agree with bobby above, some planes really shouldn't be single pilot when they are. It is not to bad when eveything is working, but lose and engine or something else serious and the work load in INTENSE!