Our gues for the rendernode is 2x X5670 or similar intel xeon procesors with 12threads for each procesor. Those are not tne newest one but the best in price\speed.
16gb or more DDR4 RAM.
The chapest there is 256 GB HDD (Better 256 GB to increase virtual memery in case of trouble with a pagefile)
1 gigabit network card
No gpu.
I love the work you are doing Necro, but you are obsessed with pagefile and low RAM, for some reason. I guess cost. For me I wouldn't build any rendernode machine with less than 32gb ram and that is if my budget was extremely limited. 64gb is much safer and you no longer need to worry about jobs not rendering or falling back to slow pagefile causing delays.
A good, reliable 250/6GB SSD for the OS will be more than enough. Probably 120/8GB would be fine too. You'll be rendering to your main machine anyway, so file storage on the node is probably not a big consideration. Cheapo basic graphics card for output (but make sure it's got display port for future-proofing!). Throw as much money as you can on the processors and lots of RAM, that's my advice to the OP.