Here you can find the expansions you can get for your farm in Harvest Moon: Grand Bazaar.
There are a total of 8 Storage expansions. The first starts at 10,000G. Each upgrade afterwards increases by an additional 10,000G for the price. The last upgrade is 80,000G. Each upgrade unlocks one additional page in your storage at home. You only start out with one page of storage.
There are two additional fields you can purchase to grow crops, trees, etc. They cost 30,000G and 60,000G each respectively. You must unlock the second field before you can buy the third field.
The basement is used in a similar fashion as other Harvest Moon games. It can grow crops from any season with the appropriate Sun. You can purchase it for 100,000G after purchasing the third field.