It is not clear that you can do this. If the money is in a joint bank account or other joint account (e.g. joint brokerage account), you can do access and use it. However, if it is his own account over which you are not an owner or a signatory, then you would have no legal power to access it without either a power of attorney or being appointed his guardian. Note that even if you are not on the lease, you can pay from your own funds, if you want, to avoid eviction. While doing that, if he is incapacitated, you may wish to seek the appointment of a guardian, whether yourself or another person, to take care of his financial affairs. You should seek the advice of a trusts and estates attorney, if possible, to advise you and guide you as to your best course  of action.