How hard is it to learn 2 languages at once (and fluency)?

If you're really willing to learn those languages then it shouldn't be too hard if you put in the time and effort. However, it will definitely be harder than just learning one. By learning them at different levels it'll probably be easier for you than if you started them all at once. I know I managed to study French and Japanese at the same time, and currently my French is near-fluent while my Japanese is semi-fluent (I started that one later). So I say go for it. :) However, I would suggest only studying unrelated languages this way. If you study similar ones it'll get confusing.