It actually depends on the quantity, frequency and how much you need the printer. I mean if you wish to print loads of documents (and frequently along the days), buying a printer is a good catch. It also maximize your time and effort as you don't need to the copy shop anymore just to copy your documents. Another advantage of it will be very cost efficient. You only need a paper and a small ink that will surely cut the copy price to only by 10% of the cost especially when you are printing huge number of copies and using it along the days.
If you're just printing small amount of documents and not frequently, it is advisable to just go to printing shop as it doesn't need much to buy one.