Note Seller Providing Sparse Details - Not Sure How To Proceed

[Ben Lake]

I am an aspiring note investor and have decided to start by brokering to build capital.  Since these are common concerns, I should start by mentioning that I have no delusions of getting rich quick, am not misrepresenting myself as a principal buyer/seller, have not paid for any dumb guru courses, etc, in other words I am setting out to do this legitimately and with realistic expectations.  I do not have a formal background in finance but I have done and am continuing to do a lot of independent study, using resources such as several graduate courses offered by MIT's open courseware platform.  I already have a primary buyer lined up who has been established for over 10 years and is A+ accredited by the BBB, and have made contact with a couple of other buyers who have indicated interest in working with me as well, so I've got some options.

Now that I've gotten that out of the way... here is the issue I'm facing. I've made contact with a prospective seller who has asked me to help sell a performing 1st SFH. The thing is, it's been like pulling teeth to get details from them, and they seem flat out unable to provide at least a couple of figures that as far as I'm aware are quite crucial to even receiving an indicative offer. They say they do not have record of the original down payment, and have provided way too wide a range of possible property value figures to be of any practical use. The tax assessed value of the property is well below the bottom of the range they gave me, and even though the state the property is in does limit tax assessed value increases based on inflation, the numbers seem pretty out of whack to me.

I'm finding myself at a crossroads now, wondering if I should just politely tell the seller that I can't provide the standard of service to buyers that I hold myself to based on the information they have or are willing to give me, or keep pushing for more information.  I have not been provided with any actual documents so far either, and rather than offer to have me sign an NDA when I asked for documentation the seller just told me that they would only be willing to provide that upon receipt of an indicative offer.  I have tried in good faith to find a buyer for this note, but after the follow-up questions I've received I fear my suspicions about this seller not providing nearly enough info are being confirmed.  I don't want to shoot myself in the foot by burning a bridge with the seller if my expectations are off-base, but I don't want to be made a fool of either.  As we know, the note space is not that big and it doesn't take much to be marked with the dreaded branding of "joker broker", and this is the last thing I want to be.  I truly do want to provide a valuable service for any buyers I work with, so I'm concerned that trying to sell a note with what seems like at best very sparse information will not do me any favors. 

Am I being oversensitive here?  Anyone with experience in this area is more than welcome to chime in, I'd be very interested to hear your thoughts on how to navigate this situation.

Thanks in advance, and happy new year to all!