Postcard

Getting a Pen Pal is easy; Go to the Socialize menu on the computer, Click: "Find a Pen Pal", Then wait a few hours. You may get a Pen Pal. Click on the Same "Socialize" Tab, Talk to them for a while, Then you will get the option "Ask For Postcard. There is a chance you will get a postcard next day in the mail.

All Postcards
These are all the Postcards and their Rarity:

Sunset Valley Common 20$

Appaloosa Plains   Common 20$

Riverview   Common 20$

Littlehaven Common 20$

Bridgeport Common 20$

Lucky Palms Common 20$

Moonlight Falls Common 20$

Twinbrook Common 20$

Lunar Lakes Uncommon 50$

Champ Les Sims Uncommon 60$

Barnacle Bay Uncommon 55$

Midnight Hollow Uncommon 50$

Isla Paradiso Rare 120$

Dragon Valley Rare 135$

==Notes=

-It is not 100% sure you will get a postcard next day in the mail.

-You Can get a Pen Pal Multiple Times

-You cannot get a Pen Pal Using your Phone

-If you don't get the "Ask For Postcard" interaction right away, try writing to your Pen Pal some more.