Sadly, the money system (which allowed you to buy and upgrade weapons) only existed in Hitman Blood Money and Hitman Codename 47. Well, it wouldn’t make sense in the storyline of Contracts and Absolution, but I see no reason why they skipped this buying and upgrading system in Hitman 2 Silent Assassin and Hitman WOA.
I hope it will exist in the next game, whenever it comes.
It exists to a limited degree in Freelancer.
I am not really fond of the side missions, elusive targets, freelancer mode etc etc in World of Assassination. Not because they are side content, but because you need to visit the same old maps again and again.
Not only does it feel unrealistic, but it also takes away the charm.
For example- The race track where I killed Robert Knoxx and Sierra Knox in the “Finish Line”- if I visit it again to kill another target, it takes away the specialty and charm of the main mission 'The Finish Line".