@Devin Chong  Just my 2 cents here and bare in mind I know nothing about this deal. :)You have a property that you can acquire for $285k that will have a $420 ARV with only $20k in rehab?  

On another note, very impressed by @richie Thomas, excellent research, I’d keep his comments in mind. I

I have never made an offer before and in my mind I think that if I lowball someone that they will get upset and react poorly for some reason. 

I'm swamped right now finishing up RE school and working but I will keep your offer in mind. I

Keep in mind I am hoping to get asking price down since property has been on market for some time.

If you have some in mind I suggest setting up keyword alerts so you can keep on top of what is going on and what others are doing.  

So by following up you mean like calling them a few days or weeks later to see if they would change their mind? I

Mindy Henderson RMLO Dallas TX

Proving what was in his mind is rather difficult.You'd probably do better suing the Realtor for his failure in his due diligence as the matter was disclosed but he failed to properly advise you and have it checked, that's why he may be so passionate .

Last thing to mind is talk with him, meet with him (or her).