If you file probate in order to transfer assets, you will also need to use those assets to pay his legal debts. If he has more assets than debt, you recover the excess if you are his only heir and there is no will. If he owes more than he has, then the creditors are entitled to a pro-rata share of what he has -- you aren't liable unless you take the money from his account without notifying creditors properly, but you also won't 'inherit' anything either, making it rather pointless for you to begin the process. (Let the creditors do it since they will be taking everything anyway!)
I'm not licensed to practice in Colorado (which is where I assume you brother lived at the time of death) so I would strongly recommend you consult with a lawyer in the state your brother lived in when he passed, as many states have provisions allowing a next of kin to be reimbursed for burial expenses etc, 'first' before any creditor can collect, but the rules are different in each state.