Yes you would have to factor in your trading cost as that will surely impact your ultimate results.
And of course you have to determine how much you feel is suitable for your risk tolerance level.
In addition to this, we are not trying to be tax efficient as our short term trades will result in being taxed at the ordinary income tax rates.
With all this said, we aim to beat the S&P 500 significantly while attempting to take less risk than this index at the same time. It's been very successful for us for decades.