What advice would you give to someone who wanted to do astrophysics and was within a year of graduating with a physics major and math minor?
That’s the degree I got! Physics major with a math minor! If your university has the option to take a concentration or specialization on the subject of astrophysics, like my university did, do that. If that’s not an option, take some astro classes, again, if your university offers them. If neither of those are available, but you plan on attending grad school, then study astrophysics. Otherwise, you can try and teach yourself.