Your friend so needs to get out of his mother's house. Do you think his grandparents or cousins would be up for it? There are probably some jobs he could get that would help him get educated as well as pay him. He might want to investigate what social security options - do they still have Aus study? - are available to him if he moves out. He might also get some ideas from whatever place he wants to continue his education with too. They (uni or tafe or mature age schools) usually have dedicated people for finding answers to these kind of problems.
I think it likely that ADHD and Bipolar are both hereditary - ie there's a high chance his mother is at least bipolar so some of the nuttiness on her part could be that.
He may also want to read Richard Branson's book "Losing my Virginity". He's a highly successful busniess entreprenuer with a very short attention span and prone to big highs and lows. If you can delegate and inspire people to work for you, then you can get things done through them even if you don't quite have the attention span to follow it through. It's like multitasking with assistance. Highly creative people who start lots of things can get them done if they can delegate.
And I know it seems silly to recommend an ADHD person read a book - but this one is easy to read a couple of pages at a time or even a couple of paragraphs. Or it probably comes as a CD or podcast somewhere. Or there are probably interviews with Richard Branson that are available as podcast.