What are you studying, and what would you like to get a master's degree in? It could depend on the field and how competitive it is. But I think that you have a good chance. Some graduate programs only look at your GPA from your last 60 credits anyway, so if you do well in your last two years and your GRE, you should have good chances. There are a lot of students who take time off for various reasons, so having a break in your education may not count against you at all. I was out of school for 12 years after I should have graduated, but didn't for technical reasons. I took another year of classes after the 12 year break, and I am now working on a master's degree. I wouldn't tell them in the application that it was due to mental illness (at least I was told not to tell that to the schools I applied to), if you can say anything else such as that you were working, or taking time for personal or family development, .... After you get accepted you can be more open about mental illness.