I'd be wary of "cheap" 10 GbE networking equipment at this point. There isn't anynthing wrong with buying used NICs and switches, but I would certainly suggest avoiding CX4. CX4 equipment is the most affordable stuff to buy into right now since the enterprise sector is dumping it, but many of the affordable adapters tend to be engineering samples that are flaky. There is also a short maximum run length and the cables can be expensive.
If someone is looking to do just a few point to point runs, at this point I'd suggest one-generation-old fiber optic NICs like Mellanox ConnectX-2s. They can be found for an affordable price competitive with CX4 gear. I'd say forget switching a fiber network though unless they can live with four uplink ports on a used GbE switch (that has 10GbE SFP+ uplinks) or have a lot of money to throw around for an all-fiber/SFP+ switch.
If they're looking toward a serious, switched 10GbE home network with growth capability then I would suggest going with twisted pair gear like Intel X540-T2 cards and a Netgear XS708E. That would get them reliable adapters which are a bit cheaper than the mainstay, previous generation X520 series and an 8 port switch. Affordable here is all relative of course. The switch would run between 900-1000 dollars and the adapters can be found occasionally for less than 400 dollars each.
Personally, I'm not made of money. heh My home 10GbE networking is fiber.