Question regarding avg bank balance and visa query

[forParents]

Hi friends,

I am planning to apply for visitor's visa of my parents. I have few questions:
1. If my parents get a visa for 6 months, from what date does this 6 month period begin? Is it from the date of the visa stamping or from the date of their entry in US..
2. Once they get the visa, what is the max number of days after which they can start their travel to US?
3. My avg bank balance for last 12 mnths is around 7K USD. Please advice if this amount is sufficient to convince the visa officer?

I would appreciate your valuable inputs.

Thanks and Regards,
ForParents

[peace]

1. From the day the visa is issued. The stay allowed is determined at US airport and is different from visa validity.
For example if one gets a multiple entry visa valid for 1o years , it means
you can enter and exit US for the next 10 years. The stay permissible on each visit is determined by the inspector at entry and stamps it on a white card called I-94.

2.Anytime during the validity of the visa.
3.Your annual income will be important if you plan to send an affidavit of support.