-Are 1911's a da/sa? Can you fire the gun with the hammer forward?
1911's are single action only. The hammer must be back to fire the gun. I'm sure there's some "custom" versions that may work differently but they will be significantly much more money and rare to find.
-Do the majority of mags work with and 1911?
???? I stick with factory mags of my gun manufacturer so I can't answer this for certain but yes for the most part? Lots of options
-How hard is it to clean compared to other semi automatic pistols?
Abit more difficult then your Glocks and Sigs, but not that much bad. As long as you're not a dumbass. Check a few Youtube videos if your completely lost
What kind of 1911 are you getting? Might I recommend Kimber, Springfield, or if your a gambler Colt