I left my software job earning $70k/year to join my dad's real estate business. I was 24 years old when I made the jump and it's been 6 years since joining him and financially it's been good for me but the business has it's ups and downs. Some years I make no profit and some years I make a million dollar profit. Some days I just want to run and hide far far away because of all the mental stress that comes with running the business and dealing with customers. Nobody can prepare you for this. Also since joining the family business, I got married and my wife hates my dad and my side of the family because of how much my dad is involved in our lives.
If I were to do this all over again I would still do it but would have liked to know what I was getting into. Treat the business as if you're buying it from a third-person and make sure your dad understands that too. If your dad is anything like my dad, it'll be hard to really sit on the "Iron Throne" and run the company like the way you want to.