Hi Marie
It may cause you problems as a joint account holder, your father should have a meeting with his bank and explain his current situation and worries and ask for you to be a signatory, you maybe able to become a joint card holder but this is a conversation your father will need to have with his bank account.
I take it you are not thinking of Power of Attorney ?
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
