Can I freeze beef bones and use them to make a broth later on?
Yes, you can.  The advantage, as you point out, is that you can collect the bones until you have enough to make a flavorful stock.  They freeze well, but will last even longer (avoiding freezer burn) if you can remove as much air as possible from the package.  I often do with with chicken bones, necks, and skin until I accumulate a decent amount for a stock.