Econ, accounting and finance courses.
Also, and this is really important and likely more valuable to your specific goals than the classes you take, read read read READ whatever you can get your hands on regarding RE investing!! You can learn a ton. There’s a whole new vocabulary you need to know intimately. You’ll also need to know about banking, time value of money, interest rate arbitrage, risk (that’s a huge one and can ultimately make or break you).
It’s a great way to make a living (a quite comfortable living) but you really have to know what you are doing. There are also professional RE investors who would entertain the idea of mentoring you.