Extensions (Harvest Moon: Back to Nature)
From Harvest Moon | Rune Factory Wiki
Unlike Harvest Moon: 64, you must get these extensions in order. Also, you may now buy wood if you end up being a little short.
This upgrade allows you to have 10 chickens, and also gives you another incubator.
Cost - 5,000G Wood - 420
Adds a kitchen (with a refrigerator) and a cabinet. You can order appliances and such for the kitchen through the Inn's phone.
Cost - 4,700G Wood - 370
Similar to the Chicken Coop extension, this doubles the animal limit to 20, and also adds another birth station.
Cost - 6,800G Wood - 500
Adds a bedroom to your house and allows you to get married! There's also a fireplace which you can chuck wood in.
Cost - 10,000G Wood - 750
The greenhouse is similar to the one in HM64, but this time it only allows for 4 plots of crops. Also, it is very easily torn down by typhoons and blizzards.
Cost - 30,000G Wood - 580