Any time you get a newer model MacBook Pro, you could set the old model off to the side and hold onto it for a little while to ensure you got all of your pictures, music, videos, and other data all transferred to your new laptop. However, what typically occurs is that you forget about the old one until much later, sometimes a year or longer, especially if you stored it out of sight in a closet or desk drawer. At this point, you obviously no longer have any need for any data still left on the old laptop, so now what do you do with it?
Humorous things you can do with your used MacBook Pro are: using it for a door stop, a paper weight on your desk, or as a TV tray to place on your lap while watching TV or playing video games. All joking aside, what many people are unaware of is that their used laptop often has value left in it, much like a used car, even if it is broken or has cosmetic flaws. What do you do when you want a newer model vehicle? You trade your current one in and get some cash back out of it to use for your down payment.
You can do the same thing with your used MacBook Pro. However, instead of trading it in and getting a new laptop at a reduced price, you sell your old model for cash. You could sell the old one first and use the cash you receive to purchase your new laptop. You might also want to wait and get the new one first, and then use the cash to put back into your bank account to offset your initial investment into the new MacBook.