I have always had 80-90% of my total net worth invested in real estate and the rest liquid as a cash reserve besides maxing out my IRA, SEP IRA or Solo 401k for tax purposes.

This is totally false. 

I live out in the Bay Area but obviously can't afford anything here, so I've started looking at markets around the country and am particularly interested in Chicago given I spent the last few years out there.

There's obviously more details to the story and lots of lessons learned here.

I'm still new to investing, but I've been told that on a multifamily property you are only able to borrow up to 70% of the total value.

@Jim Adrian, I totally agree with you on what a credit score is.

Mentors: Anybody that has done this successfully for at least 4-500 units in total, I am all ears.

It is totally doable. 

The other is much lower but is a fixer upper that would probably require work that would bring the total cost to be $140,000 with the addition of the money to do repairs. 

If you hired out any services, obviously bill for at least the cost; if you did it yourself, then whatever you feel is appropriate.