Long story short, we were supposed to partner on a deal and he backed out last minute, citing discrepancy in the ARV.

We discovered the discrepancy while going through Income/Expense reports).

I have spent hours reconciling the expenses they told me in emails with my owner statements and finding discrepancies.

I'm not saying it is the case, just that it could be, as you need to factor in the skewed branded searches in evaluating the true performance discrepancy between the two sites. 

I don't know what to do with that discrepancy.  

They have the rebuild cost to be 400k.I am wondering why there is such a large discrepancy in price.

so @Jason Thompson , rather than speculating , let me know your zip code and house configuration that you are looking for and lets debug and analyze together, every market is hyper local and can not be generalized, I've shown how in my zip code the price is actually flat and never drop unlike what they said in newspaper haha LOL the problem with housing is actual sold price is not like stock price where everyone is seeing the same chart, this is actually I think the benefit of real estate investing whre sometimes people oversell or overbid their houses due to inaccuracies or lousy realtor.I made >100k in 2021 alone for 4 months studying the price discrepancy lol

If natural gas is less expensive than electricity as a fuel source, you would a similar, though likely greater, cost discrepancy if you were to replace the gas furnace/boiler with an electrically fired one of equal output.  

I have seen some discrepancies.

Above all, don't facilitate note transactions that you are not taking an equal share in, like buying half the note with another qualified investor or a licensed broker.Frankly, I doubt any note "investor" dealer is fully compliant, I say that because I never went into a bank examination where a bank was at 100%, fully compliant operating in all areas without any mention of discrepancies, so if a bank can't do it I have no idea how small note operators could accomplish it......not unless they have a compliance officer or firm employed.