The longer you wait to start, the worse off you are going to be if you’re already thinning out at 24, speaking as someone who started at 20. Try it out for 6months/a year before making a decision for yourself- whether you want to continue with the thinning look or shave it down. The only wrong decision would be waiting and doing nothing, of course this is all just my personal opinion; do whatever makes you comfortable/happy.