@David Cozzi I recommend reading The Millionaire Real Estate Investor by Gary Keller and Never Lose a Customer again by Joey Coleman.

Purchase: Marta Brown, Blue Peach RealtySale: Eric Feng, Keller WilliamsI learned so much from them and I’m forever grateful!

Kara Johnson, Realtor, Keller Williams DC

The One Thing by Gary Keller, who founded Keller Williams, is very helpful is prioritizing and business in general.

"The millionaire real estate agent" by Gary Keller; obvious suggestion but can be very helpful.

I'd also recommend Gary Keller's The Millionaire Real Estate Investor because of the practical tips offered in the book. 

I would recommend reading Scott Trench's Set for Life, John Bogle's Little Book of Common Sense Investing, and Gary Keller's The Millionaire Real Estate Investor (in that order). 

Pick up some REI books that interest you, check out The Millionaire Real Estate Investor by Gary Keller and The Book on Investing in Real Estate with No and Low Money Down by Brandon Turner.

If you have more time than money, read The Millionaire Real Estate Investor by Gary Keller and read Profit First by Mike Michalowicz and then go out and start making offers. 

@Billy Zhao $500 should get you plenty of books, I recommend The Millionaire Real Estate Investor by Gary Keller and Never Split the Difference by Chris Voss.