I understand the prohibition on eating meat during the nine days, but is one allowed to still purchase meat for later consumption outside of the 9 days.
Certainly. At least one shabbos will occur during the Nine Days, and meat is permitted for consumption then. Until refrigeration was invented, eating meat on Shabbos meant -- well yes they had other preservation methods, but most likely people would be buying it during the Nine Days too.
Similarly someone could be making a seudas mitzva and permitted to eat meat; so he could buy the meat whenever is convenient -- or I could buy the meat for him, and so on.