I have my town arranged by building payout times, so all the buildings that pay out get put in the appropriate area. The big stuff is being dumped into my Heights area - which is the only place I have room for them. The airport and smaller stuff is in my permanent Event Zone near my Brown Houses for now, when the event is over it's going up into the Heights with the rest of the stuff unless they convert it to payout buildings. If they do convert them... I may have to break down and just buy some more land. I've been holding off buying land while I try to hit 1Billion dollars - I only have $604,136,360 so far.
