ergophobe - 6:50 pm on Jan 3, 2012 (gmt 0)
A couple of things come to mind. You could use sessions to track a given user and then the question is whether you want to rotate, or shuffle.
Rotating would be easy. Say you have 30 properties. Assign a number between 0 and 29 to each visitor and save it as a session variable.
Then every time the front page loads, you check for the variable and you start listing the properties from that number.
So a user who sees #12 on first visit would always see properties in the order 12, 13, 14... 30, 1, 2, 3... 11.