Although the most significant cost to running a Solana Validator is the SOL for voting, the hardware requirements are nothing to sneeze at. Solana’s offical documentation has clear guidlines. There are four critical considerations.
1 gbs of up and down network bandwitdh and 100% uptime. This usually means datacenter unless you have access to extremely fast and reliable network.
128 gigs of ram with observation showing 256 gigs to be significantly safer during an activity spike.
CPU with 12+cores where a single core can keep up on the PoH timer. e.g. you need at least 2.8 ghz to keep up properly.
Two extremely fast NVMEs (~1 TB each) that are distinct from your boot drive. One for the swapfile on the ramdisk that holds the accounts data and another for the ledger data.
Getting bare metal servers with the apropriate specifications can be diffcult to find but there are a few that can make sense for a validator just starting out. One solid option is going through the Solana Foundation Server Program. They have made long terms deals with a few reputable data center providers and have a reasonable cost. $600 -$800 a month with commitments no greater then a month. There are other option that are cheaper such as https://www.ovhcloud.com/en/bare-metal/advance/adv-4/ that one could explore.