You would be limited on the mill bits you could use everything would have to be light as the spindles in a drill press aren't built for X-Y movement or the bearings will suffer, then of course you will need to add an X-Y table. The Z movement seems to be by a handle at the back which is ok but you would need to make sure each time that the table hasn't moved left or right on the column.
These things can be overcome to some extent but you may quickly find that you'll need a bit more accuracy depending on what work you do also the opposite applies most people don't use Milling machines as drill presses because most of the time you want a quick hole putting somewhere and mills don't do quick!
Rudy Kouhoupt has a video on Youtube that may help a bit.
Hope this helps a bit as I've said keep it light and don't expect super accuracy and you'll be fine and lastly don't use the drill chuck to hold milling bits...