Hi,
Iam going to Us for the first time. I am planning to take my mother along on a B2 Visa. My father has expired and mother is getting the pension. Please adice the chances of clearing the VISA interview. Please also advice the documents that would be required. I want her to travel along with me. Does it create a problem if you are not in US and you are issuing a invitation letter to your parents in advance.?

Not recommend to bring her with you on your first trip... you will have many things to do yourself. It will be much easier for her to apply for B-1/B-2 to visit you later. If her income is insufficient then you can sponsor her, etc.