or if you want to buy bhp stock, at a discounted price, then there is better strategy for you.
put on a position for bear put spread, and either use ratio or sell a naked put after the short strike price to finance your bear put spread (you can usually do this for credit).
therefore when stocks goes down, you profit from it (and therefore brings down your breakeven further), and when it reached your naked put, you have to buy the stock (in case you got assign).
when the stock stay above, your breakeven, you got to keep the credit from the spread.
Much more better situation to be in, rather than complete naked.