A fiduciary duty is a duty conferred to an agent by assigning a power of attorney. According to the fiduciary duty, the agent must honestly perform their duty in your (principal's) interest. The agent should not misuse the authority of a power of attorney by using their personal resources to conduct financial transactions on your behalf. In this situation, they are not liable to pay for the financial obligation for the transactions conducted on your behalf. However, the agent will be responsible for paying off the debts if they agree to serve as a cosigner for those transactions.
The agent who has been assigned with a power of attorney also has the right to access your bank account, pay bills, and manage your debts on your behalf. This individual also holds the authority to make decisions regarding your medical care. You can still manage your affairs even after assigning a power of attorney to another agent. Remember, as long as you are not mentally challenged, the agent is liable to abide by your stated wishes.
The responsibility of a cosigner and an agent is different, as the former is presumed to hold some level of financial liability. The cosigner is equally liable to incur the debt or responsible for repaying the debt if the actual purchaser fails to pay back the owed amount. However, it will be determined based on the agreement.
If the cosigner is equally responsible for incurring the debt, then the creditors can pursue the cosigner for collection. But the creditors should approach the principal debtor who incurred the debt before collecting debt from the cosigner.
The agent can face legal consequences if they misuse your given POA. An agent might be sued in civil court or face criminal trials based on violation of the law. You could put your agent behind bars if the individual failed to perform the duties honestly set out under a power of attorney. Therefore, agents should execute their duties honestly if they don't want to face civil consequences.