Your comments are so horribly wrong I don't know where to start. But I'll try.
You are buying this as an investment property. Presumably you wish to make a profit. This is important because what the original owner paid for the property is totally unimportant to you. You don't give a damn. Period. You only care about what is the maximum price you can pay and still make money.
If the seller doesn't like the maximum price you are willing to offer, so be it. You don't buy it. If they like that price (or even better, a lower one), you do buy it. Period.
As for offending the seller, why should you give a damn? Make an offer that's reasonable to you.
The only reason you should give a damn what the other person wants is that you might be able to creatively meet their needs without putting up so much cash.
Do you actually know how to calculate whether this will be a profitable rental purchase or not? Because if you don't know - and I mean REALLY know - you would be a damn fool to put yourself on the hook for HALF A MILLION DOLLARS.
I'll be glad to supply references to books that would be helpful in learning how to do the numbers if you need them. From your question, I suspect you do.