There are 3 building upgrades that you pay for yourself that you can use on your farm
Pond: Tak can build you a pond that automatically goes in the pasture next to the big tree. In chapter 2 There is an event where you can get ducks. For more info on how to get this event see the Animals section
Cost: 2000G
Food Processing Room: This gets built next to the food storage building. Inside are 2 weird machines. One produces butter when you put milk in and another cheese. These products sell for a lot more then regular milk, depending on the type and quality of milk you use. For shipping prices of the butter and cheese, see the animals section under Cows.
Cost: 30,000G
Milking Room: This gets built behind your tool shed and connected to the barn. There are 2 doors to thee milking room. One inside the barn. And one in the pasture. Push your cows in here and they will walk along a path and automatically get milked and the milk waits for you in a little door. After a while the cows will automatically go inside themselves without you having to push them at all
Cost: 60,000G
Your House: Each chapter your house will be added onto. Making it larger for you and your family. These upgrades are automatic and free!