AT_HOME PRINTING: By far the most accessible, this is easiest option for tackling the project in smaller chunks on weeknights rather than spending hours in a studio or waiting at a print shop. However, you should test paper before buying a ton of it, printers can be especially finicky, and your can't exactly change the ink your printer uses. If your printer isn't higher end, you may have very limited paper options. Here's a little more on at_home printing.
POSTAGE and Quantities: The number one tip you need when it comes to sending out your invites, is that your guest list number does not equal the number of invites your sending. Do the math on how many couples you have ahead of time, and you won't make the common mistake of ordering about double the invites you need.