Visitor visa for my Mom..

[struggler]

Hi,
I am a graduate student in the U.S. since January'07 and enrolled in MS/PhD, which should finish by 2013, though my student visa as of now is valid till 2011.
I have been diagnosed with Bipolar Disorder and I even had to take a leave of absence for 6 months around January'08 because of an episode and return to India. I am back to U.S. now.

I want to apply for a visitor visa for my Mom, so that if later on such emergency occurs, she can immediately visit me here. In particular, I am planning to get her with me in January'09 and stay with me for about 6 months. Is this a valid reason for her visitor visa?

Also, what period do I mention in my invitation letter? Can I request to issue a visa for throughout my stay in US - till 2011 ? or I can only request for 6 months at a time?

If I am interested in showing from my side that I can financially support her, (along with financial support documents from my Dad side), nearly how much money should I show in my bank account? I do have an assistant-ship.

Please help me with the information. I have given the detailed context of my situation so that you could help me see, if I am missing out something.

Thanks a lot!

[C4us]

She can certainly try. The most important thing is for her to demonstrate the ususal ties to home country.

I would not expect your disability to influence her chance of getting the visa; it is likely to be viewed that you should return to your home country if you need assistance since you are able to travel. If you are taking your meds and seeing the psychiatrist and psycologist as required, you should not experience a major crisis requiring assistance.