The very simple answer is that you CANNOT these days start an airline with 744. There are no 744F available for sale or lease and when/if they coming on the market, your start-up airline will be number 17 in a list of interested clients so you would not get it anyway. And unless you a close relative of Royal family ruling some nice sandy country it is very doubtful you have finances to order a brand new aircraft (means bring quite some money upfront!) and then wait wait wait for your production slot.
Costs more to operate? Yes but you have no choise. Carries more payload? Not really, a proper 747-200F takes as much as 747-400BCF. Better range-payload? Yes but not necessarely you need it and even you need it, not necessarely you can use it. Burns more fuel? Yes but not so big difference and even at today's jet-a1 rates the lease price difference still almost covers this.
It is more about airline & management than aircraft type. There are companies making money with 742F, with DC10s and even, still, with DC8s and 727s!
Overall you have a choise - either you starting with 742 and then growing, stabilizing and one day taking 744s (and there are success stories), or not starting at all.