FC3: 1 day to pew pew boom. Seriously, its just watching some youtube. Yu wont be no top gun though :P ( F15,SU27,SU33)
A-10C: 1 week for weapons system give or take.. up to 6 months .. he he I learned start up last.
IMO: don't get a chopper if yu don't have pedals. It isn't right. been there done that.
mi-8 and huey are "simple" yet hard to fly properly (PEDALS PEDALS).
K-50: same as A-10C.
I recommend yu get FC3, the F15 PFM is epic and instant joy, go from there.
There's also the free TF-51. :D