probably more than you think. for the legal attempts i'm guessing the nps might have some estimates. ???
anyone who's already set this goal should really already know what these might be ... and be prepared to face and deal with and/or walk away from them. (btw, reading the solo permit application might be helpful in providing some food for thought.)
that's an incredibly subjective question, and (like others said) it really depends. there are so many factors that come into question when making this type of decision, and if you haven't tried to think of and through every one of them before coming to terms with it (and it's possible consequences), i would venture to say that isn't so wise. but there's plenty of time between now and then to gather information, assess yourself, and make your best decision.