700 square feet? That's 65 square meters, who even wants that much space for one person? A good-sized flat for a person here has around 40 square meters, so 430 square feet. Insane.
My dads tiny home is 10x10 feet and has a second level which is really only 4 feet tall mainly for sleeping a tv and a dresser. The place is perfect for a single person. He went with closed cell spray foam and the place can be heated on a candle practically. It has a toilet and shower, mini fridge and sink. I will admit storage is a little tight but as for living space perfect for a single person. It was made to be extremely energy efficient and with climate change I think we should aim to be more like it not have some minimum.