I think you are on the right track however its going to be necessary for you to have some "skin in the game" sooner rather than later - while it can be appealing and seemingly possible to build a significant real estate portfolio with all of "OPM" the reality is you are probably going to need to have some equity in these properties - 20% or so down from your own funds to keep building. 

However, I feel this won’t be for another few years and I want to start building my portfolio sooner rather than later.

The sooner you have them in your name the better.

The sooner you can complete your purchases, the sooner cash flow is restored to you.  

Trying to be an investor when you don't have personal finance discipline is like going to a cross fit gym when you drink beer and eat fried garbage every night. 

Most of the amenities an apartment complex offers larger universities have on campus (gym, pool).

You'll regret not starting that sooner than later. 

@Sherri O'Neal -- as the other posters here have commented, you can absolutely get started now -- but the sooner the better.

They avoid the eviction and you get the unit back sooner with less hassles. 5.

I wish I had known about it when I was younger because I likely would have bought my first house much sooner.