Graduate School? Or Real Estate?

[Jonathan Escobar]

I'm 23 years old. I've always wanted to be a dentist since high school. I am in my 2nd year of college getting ready for my 3rd out of 5 years of undergraduate. I'm planning on majoring in Marketing and completing classes to apply to dental school. By the time I become a dentist, it will be 7 years. By that time, I will have around $300,000-$400,000 in student debt. Dentists make around $120,000 a year on average and can make more than that. 

My brother is planning on investing in dental practices which he tells me are VERY PROFITABLE because there is a barrier of entrance only for dentists. He is planning on retiring at age 35-40. I am 23 years old. I am planning on finishing undergraduate at least, but I need some help deciding whether I could reach financial independence before that if I don't take on a lot of debt even if I will be making a lot more money from W2 job. 

Does anyone else have this dilemma? I've seen how hard my brother has had to study to get into dental school and to graduate and it just looks tough, though I am willing to do it while investing in real estate on the side and house hacking to get rid of my living expenses. How could I reach financial independence before he does?