Witnesses aren't like miners. They don't "mine". They get scheduled for a block, and when the time comes, they just broadcast the block with their signing key, and the rest of the network goes "oh it's someguy123, he was supposed to broadcast this block just now so let's take it".
Because of this, witnesses don't need "mining equipment". Any run of the mill dedicated server or VPS is perfectly fine. You're mostly looking at network connectivity. You want a provider with DDoS protection (so if you, or anyone else on the host gets attacked, then your witness shouldn't be affected), and a large network. OVH and Hetzner both fill those gaps these days. DigitalOcean is also pretty good, but expensive.
You also have to be aware that miners and witnesses get paid in STEEM Power. Even though I'm currently getting 1500 SP per month, my ranking changes a lot, and my current total of 5000 SP / 104 weeks = just 50 STEEM per week, it's not that profitable until I rise up some more.
I can't tell you much about the mining system in STEEM, but it's very different from Bitcoin. Instead of mining blocks, you mine account private keys (ECDSA instead of SHA256), and if you successfully mine the key, you become a witness for 1 block, allowing you to get 1. a new account of your choice (that's why badger has like 100 badger[1-9] names), and 2. 1 SP from the block. (I'm not 100% certain of these, someone correct me if I'm wrong)
Thank you for replying, Just one more question. What kind of expenses do you have and how much?
The server my witness operates on costs about £30/mo (thats $40 in US Dollars). That server runs several other things (but all isolated on different networks within VMs), but the witness is still fine.