Here, the September 16th 14 long call stands in for the stock (since it's mostly made up of intrinsic value), against which I sell calls to reduce my cost basis in the long option over time, the goal being to take off the entire setup in profit when the total credits collected for the short call (and any rolls) + the current price of the long option exceeds what I paid for the original setup.
Here are the metrics:
Sep 16th Long Call/April 15th 21 Short Call
Probability of Profit: Unknown
Max Profit: Unknown
Buying Power Effect: $585/contract (debit)
Unfortunately, the probability of profit and the max profit are unknown for this setup from the get go, since exactly how much credit you can collect for the rolling of the 21 short call in the months after setup is unknown and will vary over time. It is also possible that, depending on the price movement in the underlying.
I would also note that VXX , by nature, generally suffers from contango, so its price will naturally decline over time in the absence of backwardation. Consequently, it's entirely possible that price could break 14 at some point going forward. Naturally, that's okay as long as the amount of credit you receive for the rolls of the short call exceeds what you paid for the long call (currently, $745) and, of course, I'm assuming that price in VXX will be somewhat above 14 for the duration of the trade.