You need to consider the maket value of the property. That requires some research. You can hire a buyer's agent to do it for you, or you can use the many online services to find properties like the one you want. Once you identify properties like it, see what others have paid for them. Then you know what you "should" pay for it. Negotiate from there and you'll do well for yourself. The link explains this in more detail.
It is also important to take into account the time on market for the home. Sellers who have just gone to market will be more firm on their price (whether it is reasonable or not) the shorter the home is on the market. In addition the seller motivation is important a transferee has a different mindset from a retiree.
Consult with your agent and take a shot, Keep the negotiations moveing quickly, and get the home you want!
If they owe $465K for it still on their mortgage for instance, you likely won't be getting it much lower than that.
But if they only owe $300K on it, then maybe you have a better chance at getting it for a lower price. Just a thought. Thanks, and good luck,