I sort of agree with Kthomas. Unless you actually inspect the records before you buy them you really don't know what condition they are in. For all you know they could be totally trashed and valueless, even those rare typically highly prized ones. If I were buying them blind, based on the condition I have seen most typical old vinyl in I'd be hard pressed to offer much at all.
What might be something fair to both of you is to actually inspect the records, cherry pick the good ones and offer him a fair 'wholesale' price for them and offer to dispose of the rest for him. (Include in your offer the value of the time you need to inspect the records and dispose of the ones of no value.)
BTW, if he mentioned the old 78's I suspect he already knows that they have some value - most folks wouldn't think old 78's would be worth anything, unless they just loved the music (and they had played the record endlessly right up to its demise).
Hope that helps a bit.
What might be something fair to both of you is to actually inspect the records, cherry pick the good ones and offer him a fair 'wholesale' price for them and offer to dispose of the rest for him. (Include in your offer the value of the time you need to inspect the records and dispose of the ones of no value.)
BTW, if he mentioned the old 78's I suspect he already knows that they have some value - most folks wouldn't think old 78's would be worth anything, unless they just loved the music (and they had played the record endlessly right up to its demise).
Hope that helps a bit.