FWIW I spent the money to get to level 4 and think thats probably as far as I go with the IRS. Its radius is 8x8 I think, which is about 1/8th of most peoples whole towns. My town is bigger than most I see on here so its a good level to settle on. Theres really no incentive for me to advance to level 5, For 1.) it costs $1,000,000 I think, and do I really need a blue IRS vs red for $18M at the last level? No, I do not.