On Urbana Spes City, all flats and houses have been reduced to 10L$ per day for 100 prims. You can buy more prims in units of 10L$ per 100 prims by IMing Mercia McMahon. See Mercia McMahon's Profile for details.
Urbana Spes 128,128,302
Note that these are residential only rentals, there are stores to rent, but they cost much more.
50 prim stores 50L$ per day
100 prim stores 100L$ per day
150 prim stores 150L$ per day
200 prim underground rooms 200L$ per day