To know the value you would need some historical data, and some very good management cost numbers.

I don't see that as a bad thing, with precautions taken to ensure amicable splitting down the road. 

So I can call customer service and in 3 minutes get a complete verbal date down on the phone.. it helps in real time when your working foreclosure stuff.Also any agent can call customer service and get copy of last recorded deed the tax info zoning etc.. sent over in a matter of minutes... out east when its kind of backwards form what I have experienced were you open an order and they don't order title to the end as you have to actually pay an abstractor to go to the courthouse I guess and physically pull data... so this leads to title issues at the end of the transaction were out here we have title within as I said 72 hours max of opening the order so you know up front if you have an issue and you have the whole contract period to work on it if need be.

The way to maintain your negotiating leverage is to ensure you're able to close on the purchase if you need to.

The Agent gave him all the comps and data he could ever want.  

You can figure out their rental history from public records using beenverified.com and/or your local court websites.I usually just do the latter; If they don't have any rental judgments or a criminal record then that is usually a good sign and if they do then you might want to think twice.So what does beenverified state with regard to use of their data and compliance with the FCRA?

So, if I let the buyer's option fee clear the seller's account first, how can I protect my interests (and ensure I get paid my assignment fee from the seller)?

Here's a few links:http://www.newyorkfed.org/householdcredit/2014-q2/data/pdf/HHDC_2014Q2.pdf http://www.rcm.company/non-performing-notes/

I told him that would change my criteria and it would no longer be the list of data I'm looking for.  

The websites tend to be more accurate in more densely populated areas because there are more data points.