If Can Only Use Free Resources To Comp In A Non Disclosure State How Can I Do?

No paid programs. No matrix mls. How could I go about it to use as negotiation? Right now my strategy is to use privy adn only use the mls data. However. That is all I am using it for and I am trying to penny pinch. What if I did it where I started with a free platform like zillow or redfin even in a non disclosure state, then actually use that to my advantage by telling the agent (I only work on market) that if they think I am way off with he numbers could tghehjy provide me comps of their own thus throwing the ball in their court and then tell them that before we finalize the deal should we get there that aI will run it past some of my real estate agent partners to validate it and as long as there is not a crazy discrepancy I will accept it as the comp as part of the final purchase price.