Houses are used to create and maintain villagers. The villagers can be used to perform jobs such as a Worker and a Hauler and feeding dinos.
There is no difference between orange and blue houses in either price or build time. They are only different in the time period between collecting taxes. Usually blue houses give more but take longer time to generate the taxes than orange houses.
To upgrade a house, please refer to the requirements for the next level of house. For example, an orange house can not upgrade into an orange cottage if the village does not have a Big Rock (Level 2) and you are at Level 4 in the game, even if you already have all the price requirements.
Villages can only build a limited amount of residences. When playing Tiny Village for the first time, there are already 2 Houses, one belonging to Rupert and the other to Regina. Any house after that can only be built by raising the number of house slots or building gold or purple houses.
There are some ways to raise the limit of house slots
Many of the Stores can raise the limit by one or more. Refer to the Stores page to see how to raise the limit
Some Decorations also raise the limit, for example:
By comparing the cost of upgrade to directly creating the highest Mansion, the most profitable way is to directly create a Mansion. Unfortunately, in lower levels, you will probably already have some Houses, Cottages or Villas, so these houses should be upgraded to Mansion to give a bigger investment and not wasting all the build resource.
The following houses are limited to certain themes and are only available during certain periods. See the details on each house for more information. They are generally not upgradeable.
Note 1: Please note the "cost" of the House as noted above are their nominal values set by TinyCo. The real cost of each house is the you actually pay to get it during the related event.
You can put a house into inventory but you need to exercise some caution:
The house slot counter will decrease, allowing you to create another house so long as you haven't exceeded the limit on the number of houses.
All villagers inside the house will also be removed from their work and kept in Inventory along with the house. If they are working on something, you'll need to assign other villagers (if available) to their tasks.
Warning : If you put a decoration or store that adds a house slot into inventory, the house limit will also be decreased. So it's possible that you can get a "red limit", meaning you have more houses in your village than the number of permitted house slots.
The effect of this is you can not buy any more houses until the house slot limit becomes larger than the existing number of houses in the village (by adding various stores or decorations to the village).
Sometimes a weekly challenge will present a limited availability decoration that will add a house slot. For example, in Holiday Week 2012, a Snow Fort was offered for sale ( 50,000, 3 x 3, +1) and the Harvest Week Theme offered the Harvest Barrel ( 15,000, 2 x 2, +1).
A house slot is also added by the first Wonder Challenge, Stonehenge ( 30,000, 5 x 5, +1).
A handful of decorations have added two slots per decoration, such as the Snow Globes.