Update.  I did spend $10 dollars which gave me 10000 UPX and I have collected the king of the street collection.  Three properties in the same block or street.  2532 Cabrillo st. which was my original purchase.  The collection has boosted the UPX from 47.52 to 56.16.  2526 Cabrillo st was purchased for 3750 UPX and brings in approx 70.2 UPX a month.  2512 Cabrillo st. was purchased for 4200 UPX and brings in appro 78.62 UPX a month.  This has boosted my collection of UPX by 1.3 for each property.  

The other two properties are 1158 Key Ave and 782 27th Ave.  I hope to add one more property soon so I can get the San Franciscan collection which must include 3 properties within San Francisco.  Currently my UPX stands at 407 and I collect approx 20 - 30 UPX a day.  This brings the grand total to 5 properties for a UPX property total of 15,837.  

One of the best aspects of the game is the street level view.  Just pick a property and click the street level - a 360 degree view allows you to get a real world picture of what the exact area looks like.  I have found one inside of a building.  This detail really allows the viewer to get a wonderful, intimate look at the nitty gritty side of San Francisco.