You can have low-cost commercial grade services run using off-the-shelf hardware.
pfSense includes support for CARP, which lets you build high-availablity failover clusters. You can have two (or three or four...) cheap systems and if one dies, just fix/replace it as needed. The backup system(s) automatically take over and nobody would likely even notice the changeover.
When it's cheap, that is much easier to consider.
If you want no moving parts, you can use an ALIX box, Soekris, or perhaps even some atom-based boards. If you want to use server-grade boxes to make yourself feel warm and fuzzy, you can do that too. Supermicro even has a server-class atom board in a 1U rack which runs pfSense very well for us.