When you get to the mission "The Belgian Problem", you should first make a save because there are two achievements for this mission and this will save you a second playthrough. At the end of the mission you'll get a choice: blow up the building or keep it for yourself. If you blow the building, you get a permanent 10% bonus on all future reputation earned. If you keep the building, you get a 10% bonus to all income earned. To get 'Tower Defense', choose keep the tower. To get 'Kuh, Boom', choose to blow up the tower.
I personally find keeping the tower to be the better option since your reputation caps out at 50 and if you keep up with side quests, activities, assassinations, etc, you'll probably be in your 40's by the time you're getting into Act 3, but you can always use more money for more upgrades.