Council paying 'non refundable' deposit?

Tenancy Deposits

I have had an enquiry for a two bedroom flat from a young lady who is at the moment in a refuge. She has one young child and has one on the way. She tells me that the rent (£460) is within the Councils limits for her.
She says that she doesn't have a deposit, but that the Council is willing to pay a 'non-refundable' deposit for an AST of 12 months.
Has anyone heard or had experience of these and how they work, or if there are any special conditions attached.
I just want to be forewarned, I cannot find anything on our local Council website.
Thanks you.