The types of courses (and what the requirements of those courses will be) will depend on the particular academic program. You'll have to ask the school for that information as you do your research on particular programs. Most Master's Degree programs have a combination of requirements that include tests, papers, clinicals, etc. -- and whether they are "hard" or "easy" depends both on the particular school and your particular abilities.
Personally -- I went to a very rigorous undergraduate program and felt that my Master's Program was easy in comparison. However, I have had friends who had the exact opposite experience.
As far as income goes ... again, that depends on your particular situation. You might see a drop in pay if you are now working as a staff nurse earning big differentials for night shifts, weekends, precepting, etc. and/or are able to work overtime hours. If you take a salaried job at the Master's level, you might get a higher base pay rate, but get a smaller paycheck because you don't get overtime, differentials, etc.
However, if you are fairly low on the staff nurse payscale and don't get a lot of differntials added to your pay, you would probably see and increase. A lot would depend on what type of job you get. What type of job would you be seeking? What types of employers
would you be looking to work for?