In the vast majority of cases, we offer to buy (purchase) the property from the present owner.

In all cases including those involving money, this is merely a form of exchange or barter.  Whether it be chickens, goats, or dollars (or some other medium of exchange), we have something we are willing to give him, if he will give us that property of his which we happen to want at the moment.

If we are astute, we will offer no more of what we have than is absolutely necessary in order to convince the owner of the property to transfer ownership of the item to us.

In fact, if we think we can get him to give it to us for nothing, we might make that attempt.

There is nothing immoral about offering a low price (and zero is about as low a price as you can offer).  If the owner will not accept zero, then we begin raising our offer, until the value to ourselves of what we are offering exceeds the value TO US of what we are seeking to acquire.

Hopefully, we will quickly reach an "exchange plateau", or that point where the offer is high enough where the owner will accept it, and still low enough so we will (and be able to) pay it.