|Raspberry Pi 3 Model B/B+||$30 (either model B or B+ should work fine)|
|8GB or larger MicroSD memory card||$5 eBay|
|USB Power Adapter||$5 eBay|
|USB to serial RS-232 interface adapter||$5 eBay. Make sure it is Linux compatible.|
|Serial RS-232 null modem cable FEMALE/FEMALE||$5 eBay|
|Total project cost||~ $50|
You can also choose to use a Raspberry Pi Zero which will save you some $15 from the total price, but for the sake of simplicity, we'll be using the Raspberry Pi 3 Model B on this tutorial. I've only tested these two Raspberry Pi's, but I see no reason why Virtual Modem wouldn't work with any Raspberry Pi or even other Linux platforms. If you have success with the other platforms, I'd love to hear from you!
On to the next part!