I was wondering about upgrading a building or certain buildings. A building would only allow up to a certain passion level. This would help as a money sink so you don't end up with $15,000. So for example the first massage building is say at a bronze level. When they owner lands on it again, they can upgrade it to a silver level for say $2000. When the owner lands on it again, they can upgrade to a gold level for $2000. So for example a bronze building would allow up to passion level 4, silver up to 7 and gold up to 9. Also, higher level buildings would receive more rent.
I think this would make the game more interesting in that each person may work a little more in order to save up for the higher level buildings. Worse case scenario is that the people are at a passion level 9 and land on a bronze level building so get a level 4 activity. This could be made as an automatic upgrade if they have the money available. Where you just send a notifying message saying your property has just been upgraded.