Depends on what you want to run. If you're trying to run all the things (Core, LN, electrum, mempool, etc..) then 16 gigs of ram bare min. My nodes' CPU is an i7. But bare min I guess if you're just doing core and LN then like 8 gigs of ram maybe 4, but it will be slow and clunky with 4. CPU...something like equivalent to an i3 \ i5. Not sure where you're located, but on eBay in the US an older dell optiplex with decent specs can be picked up for under $100.

Benefits are using LN in a self sovereign fashion. If your node is well-connected enough you'll earn some sats from routing but don't expect *any* form of profit unless you are spinning up massive channels. I mainly run a node becasue I dont trust 3rd partys and I wanted to learn about LN.