Since you've been thinking of manipulating the WM to maximize tarrifs, I guess you might be inclined to manipulate with the crime fighting setting, too. Crime fighting works like this: At 100% setting, a crime building will be removed at the 1st of every month. At 0%, you'll get a new crime building at the 1st of every month. At 50%, you'll have an equal chance of gaining and/or removing a crime building (not 100% sure about this).
What you do, if you're short on money, is that you leave the crime setting at 0%, except for the 31st of every month, when you raise it to 100%, let one day pass, and thusly remove one crime building/avoid getting a crime building. On the 1st, re-set crime fighting to 0% - full crime fighting for 1/30 the price!
There's one downside to this, though: 0% crime fighting doubles revolt risk, so it's advicable that you raise the setting to at least 50% at all times and 100% in the end of each month as soon as you can afford it, at least if you have problems with lots of revolts.