I'm a small timer in this game still struggling to get anywhere with this as the daily earnings in this game are quite slow and it takes patience to keep growing one property each week.
With that said, I'm starting to see more visitors now to my properties too which is beginning to help a little bit with additional UPX earnings. It's still small scale for me but actively trying to find some more ways to get my UPX earnings up.
Next, I might try treasurer hunting too.