"Immediately" per the title, mortgage refinance loans and many other consumer loans are covered by the Truth in Lending Act providing a Federal 3 day "right of rescission", where you can cancel the loan within 3 days and owe nothing.
Pennsylvania separately provides a 3 day right to rescind for any contract over $25 where a salesperson called or came to your house -- I exercised this with a door to door privatized electricity seller who would not leave. I finally accepted it and rescinded the next day.