Joint Sponsor Paperwork

[adapalam]

Hi,

We, me and my husband are planning to invite my parents here.
We both are on H1, and we have our own bank a/cs, but we don't have substantial balance in them.
Together our avg balance will be around 4000$.
Can we go for joint sponsorship? If so, what all additional papers, statements etc are required?
I have tried looking up for paperwork for joint sponsoring, but could not find anything.
If anyone can plz tell me what the requirements are or direct me to where I could find them, it would be very helpful.

Thanks in advance,