1.How long completing your ASN takes depends on the school. In my particular case it took me 3 years once I was "inside" the nursing program, I had to complete my prerequisites before considering applying to my nursing program. I find most schools
ask for a entrance exam for example;the TEAS, Kaplan, NLN etc. However I would suggest that you first look for schools in your area that offer nursing programs
and then research what are their requirements for entrance.
2. I am not sure if you can work
as a Student Nurse . What you can do is while in your perspective nursing program, apply to hospitals that offer internships;they will often have requirements, a certain GPA, recommendations, essays etc. Most of the internships I have seen in my area only offer them in the summer, so you cannot not live off what you earn in those months(if you get paid). Again I do not know about other areas of the US.
3.I'm not sure I understand what you mean.Some schools will require you to purchase a review course before taking the NCLEX, other will integrate the program throughout you nursing school
career or only the last couple of semesters, and others will recommend a course but won't make you take one. All schools have their own plan. In the end you will sit for your NCLEX and if you pass you are now an RN,if you fail you must pay to take it again and see if you pass the next time. There are whole threads of students nurses who swear by different methods, reviews, books,etc. However you shouldn't really worry about this until you cross that bridge.
If you can I would also suggest to go straight to your BSN,not specifically because it is better, but because in increasing areas of the country it is now a requirement before applying for a job.
Good luck on your journey to becoming a nurse!