My neighbor's mailbox and ours were in just terrible condition. The mailboxes had a wooden cover where the birds loved to perch and poop all over them. I asked my neighbor if he would be interested in sharing a double mailbox post with identical mailboxes and he agreed. Little did I know that none of the major home improvement stores sell a double mailbox post, unless you want to special order one for hundreds of dollars or have one custom made. This project cost about $100, split between the two of us...$50 each, not too bad!
Wooden post from Lowes-ours is not listed online but very similar to this one
Gibraltar Bronze Mailbox from Menards- ours cost $34
1- 1 by 6 piece of wood approx. $5
We installed the post and then put about a 26 inch cross piece to set the mailboxes on. The size of that piece of wood will depend on the size of your mailboxes and how close you want them together. If you have any questions on how we installed it, comment below.