antpool has 16.7% of the network with 550peta
works out as about 25peta if you want a good chance of 1 block a day
although luck plays a hand in it and having more hash increases the chances.
but without getting too detailed in all the if's and buts/ luck/chance/competition... if you stick to say 25peta
it works out as about 1800-2000 bitmain s9 asics(13.5th).
.. based on very simplified quick maths. as there's no point trying to do accurate maths because there is no 'guarantee'.
like i said its based on averages, luck and chance.
Thanks.
I consulted elsewhere and we determined that to hit 1 block a week, the real minimum is around 75 bitmain s9s.
The guy I'm asking for's goal was only 1 block per month, however, but I won't give him advice at any lower than 75 bitmain s9s with proper upgrades as necessary and no expectation of actual earnings.