Standard Purchase And Sales Agreement Do You Have To Have Earnest Money To Make A Purchase And Sale Agreement Contract Legal (Real Esate)?

Do you have to have earnest money to make a purchase and sale agreement contract legal (Real Esate)? - standard purchase and sales agreement

I read a lot about buying real estate, and I wonder what you really really need to make money, a standard purchase and sale agreement legal? Or you can do without a lot of money and still legal?