unity farming game

Recently I decided to break away from my usual turret based games and decided to fill a request to build a farming game. As I started I to build a layout I realized this might be beyond my skill level. So I began to comb the internet looking for tutorials but there are NONE anywhere. So I would like to know what I need to do in order to get my farming game off the ground below I list some key features

-The game is open world with a FPS camera and a collider attached to the camera(done)

-The open world map is on a terrain(done)

-There will be buildings for certain stuff(supply shop,vehicle shop,ect) the play can go up to these buildings and a GUI text will appear saying "PRESS X TO OPEN" which will open a canvas or something(havent decided yet)

-The player should be able to buy certain land by going up to it and a text should appear saying "BUY $PRICE"

-Player should be able to plow the land -Player should be able to water plants -player should be able to plant seeds

These are just some key features that I currently have no exp on how to make happen so any help would be appreciated