If you have been using computers for any amount of time, you may have an old desktop that can be used with pfSense. Even if you do not, old desktop computers can be purchased relatively cheaply ($100 U.S. and under). For example, a brief web search resulted in me finding an HP Compaq 8100 Elite desktop system with the following specifications:

• Intel 64-bit i5-650 processor; 3.2 GHz
• 4 GB RAM
• 500 GB SATA hard drive
• DVD-RW drive
• Expansion slots: 1 PCI-e x1; 1 PCI-e x 4; 1 PCI-e x 1; 1 legacy (32-bit) PCI

As you can see, this system, which costs less than $100 U.S. (including shipping), easily meets the minimum requirements for a pfSense system. Three of the four expansion slots will accommodate a multi-port network interface card (there is also an on-board Ethernet interface). Moreover, the i5-650 supports AES-NI encryption (in fact, as a processor based on the Westmere microarchitecture, it is one of the oldest Intel processors that supports such encryption); therefore it will be compatible with pfSense 2.5.

There are drawbacks to using a desktop system such as this. The power consumption will be that of a typical desktop computer. In addition, the hard drive is a typical SATA drive; the mean time between failures (MTBF) for traditional hard drives is about three years, so the possibility of a hard drive failure is something to consider. Using a thin client rather than typical desktop computers addresses these two concerns, as their power consumption is lower than that of desktop systems; moreover, they typically have some form of flash storage or solid-state drive (SSD), which should be less likely to fail than a traditional hard drive. Still, using a desktop computer such as this for pfSense is a reasonably low-cost option.