OCI employment proof for House Wife

Hi,
I have been reading the forum to gather information about what documents I will need to submit for my wife for the OCI application.

1. Is a simple letter stating that she is not working enough?
2. Do we have to submit any additional proof for it?

She is a housewife and we hold a joint bank account. I read on a thread that 3 month bank statement might be required, but in that case, it would be our joint bank account.

So a bit confused on what is the actual requirement.