FSBO vs ARV

[Matthew J. T.]

I've been searching countlessly to find an answer for this, my question is that, well I guess two questions.

First of all, if I find a seller that is putting a property up for sale for 185k for example, and the actual ARV is only 150k, how do I go about telling the seller that you are selling this property for way too much to start at ? If you follow me, you have to be able to make a deal starting at the ARV not at what the Owner is trying to sell it at correct? Or do I negotiate with the owner based off of what there "Set" price is , or do I negotiate based off of what "ARV" is?

Second, I've been spending time researching how to find comps, even if you go based off of ARV and not what the seller is trying to sell the house to you at, and all the websites (which I have seen other people on here as well on BP) often have inaccurate information such as zillow etc (the free/computerized websites) And so if I don't have access to MLS or know anybody, what can I do about estimating ARV of a house?

I know there are "pay" websites such as RealQuest and SiteX but I am just starting out as of now and they seem to be expensive and I have searched just about everywhere looking for my answer so hopefully I can find it here. Starting out what is the first method you used without having MLS getting a contractor or paying expensive websites to figure out ARV?