lease or bonafide letter? ( staying with brother)

[Mudita]

Hello All,

I need immediate help.

I have to attend interview next week.

all i have is common bank accounts..... I have been added into my husband's Medical Insurance but my cards have not reached me yet... they did a mistake in my name and it had to be re-issued again !!

I stay in my brother-inlaws house... Can you please tell if I get a lease or we get a bonfide letter signed by my brother-in-law..

what are thier formats !!

What can I further take to make the case stronger?

regards,
mg