why do the houses for premium houses keep changing on website before can complete upgrade?

[Rolig Loon]

No, it;s not a web site issue and it's not broken.  This is the real estate market, just like in RL.  Some days, the style you are interested in just isn't on the market.  Linden Homes are "starter homes" for many people, so owners tend to trade up and move on after a while.  When they do, a house becomes available, where it might not have been the day before.  Some styles are popular enough that you may have to wait for a while for a vacancy.  Fortunately, you can abandon a house and choose a new one up to 5 times a day until you find one you like.

[Rolig Loon]

No, it;s not a web site issue and it's not broken.  This is the real estate market, just like in RL.  Some days, the style you are interested in just isn't on the market.  Linden Homes are "starter homes" for many people, so owners tend to trade up and move on after a while.  When they do, a house becomes available, where it might not have been the day before.  Some styles are popular enough that you may have to wait for a while for a vacancy.  Fortunately, you can abandon a house and choose a new one up to 5 times a day until you find one you like.