I'm quite a new Witness - only since the End of May. For longtivity you really need a server with 64gb Ram and 500gb SSD minimum, just to account for the rapid expansion of the blockchain.
Majority rent a VPS from the likes of https://www.privex.io but anywhere you can get a server of suitable spec will do.
Difficulty - this guide https://que.com/howto-setup-witness-node-by-yehey/ by Witness @yehey is probably the simplest to follow.
The biggest struggle is getting Witness votes - because blocks are dished out based on the Mega Vests your voters have - so it's not the number of people who vote you - it's the amount of Steem Power those voters have. https://steemian.info/witnesses lists the ranks, to work out potential earnings the formula is 33MV get's you one block per month.
I hope that helps, and thank you for that Witness vote - I'll free a slot up for you if you Start :-)