Advice you'd tell your younger self starting out in REI?

[Brian Pink]

I'm going to be transparent and see what kind of advice and wisdom I can get. 

My goal is to have 80-100k passive income off rentals in the next 5 years. I'm not sold on single family, duplexes, or multi family, but  really leaning towards multi (apartment complexes) for the sake of easier management and having all units in one place. 

My experience is mostly in sales and management but I've always had a knack for business organization, i'm patient for the right deals, dedicated enough to achieve my goals, and I learn quickly. I have flipped one house, (it was a purchase I made wholesale and sold it a week later). 

I currently own a welding business that I work 6 months a year (84 hrs a week) and take 6 months off. I make around 100-120 per year and have almost no debt (500 a month). 

Here's my question;

If you had the same financial/work situation and wanted to have 80-100 passive income, what would you do, knowing what you know now, to achieve the goal?

What books, videos, education would you recommend? 

Thank you for taking time to help a young investor-it means a great deal to me and my family!