Don't worry, this is not illegal, and their are no hacks, or cheats or download necessary.
First, make sure you have the latest version of tiny tower.
You will have to do this process after each update.
Two: let the game load with internet connection. play the game, and go to menu>settings> make sure everything is checked off.
Three: press the home button (do this step really quickly), turn off your WiFi using the power widget, that is the fastest way to do so, and then turn the game back on.
**Make sure you don't exit the game, only press home to exit.
you are done!