Time is really of the essence and he needs to get the ball rolling or lose $30K. 

, they're more likely to work with you if you build a level of trust, and that may be built simply by listening as @Joseph Ball says.

You never received the rent  ,  Throw the ball back in their court , send the pay or quit . 

Don't do the wrecking ball style that you see on TV.

He was ok except that towards the end when we were going to settlement I felt like he dropped the ball and I was running around emailing documents and it got crazy but it turned out ok.

@Joseph Ball I love that tactic!

To walk away without owing anything, a real estate agent would need to get him 89K or probably more likely the low to mid-90s if there is seller closing assistance.I would start with a ball-park estimate from a large wholesaler. 

Joseph Ball where do the banks disclose the upset bid?

I Would not low ball, nor would I go over asking price. 2, Comps are similar since it is multifamily rather then two attached single families.  

I learn by DOING, and I'm sure you will too... at the very least the mailing will get the ball rolling for you and get you some experience talking to potential sellers.