That depends. If you intend to catch it using the liberty pass it will be level 15. If you are receiving it through the Wi-Fi event that is currently in progress, it is level 50.
It's from team plasma i think they use it when they are on liberty island because the Pokemon Victiny is there and you need the liberty pass to get there because it's a special event and Victiny is a special Pokemon and team plasma want's to capture it so they can use it for evil you know how they are :p
krookodile evolves at level 40 in Pokemon black and white
Klink evolves into Klang at level 38 on Pokemon Black.
futachimaru evolves at level 99 in Pokemon black and wight
Level 64
Level 43
Level 5
krookdile evolves at level 40 on both Pokemon black and white
Roggenrola evolves at level 25 into Boldore on Pokemon Black.
the only level one pokemon you can get is pokemon from eggs.
In Pokemon Black AND White, Dewott evolves at level 36. Hope this helps!
Archen evolves into Archopes at level 37 in Pokemon Black, hope this helps :)