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You can take a look at above requirements and calculate cost of such setup by yourself.
Steem is a DPoS, not PoW, so there's no classic mining here.
Hardware is cheap. It’s people and their skills that cost money. You can be technically a witness just by running a Steem witness node, but block production rewards depends on how high you are on the witness list and that depends on power of votes that were cast on you... and votes depends on your engagement in the platform. So it's not really a passive income where hardware works for you.
But Steem is special in many ways.
As they say "Blogging is the new mining"(TM) ;-)
A successful blogger can earn more rewards than a successful witness.