You have zero protection if you pay with btc.
Even if you pick it up in person then drive 10 kilometers or whatever back to your home.
If it is doa or it breaks in a day you paid in BTC you will not get your money back.
S-9's Break a lot.
1 BTC is a good price but lets do a cost for your roi.
here is free power and 2% difficulty (at 3 or 4 % you are worse off)
along with a free psu you need 180 days before you break even.