Then tell him you might be persuaded to buy the truck after he gets it done himself. If that’s a problem for the seller, that’s a red flag IMHO.
You have to do a more in depth examination like dropping that pan(how I hated those 40 bolts) & valve covers take a look at those bearings. Like with anything used it's 50/50 unless it has a great maintenance history. Is the asking price good for you or can you negotiate to a price that is good for you. How much work if any do you have to put into it to get it where you want it. The question you have to ask is it worth it