My feeling would be that as long as you're not trying to convince him that they're "probably worthless", and in fact are giving him a nice chunk of change for the collection, there is nothing ethically wrong at all.
Say he has 100 records and you're going to give him $5/each, or $500. From his perspective, he just got $500 for something that was just taking up space for him, and with almost no effort.
From your perspective, you're getting a fantastic deal - again, coming into some great vinyl for a fraction of the market value. While this may seem like it's taking advantage of somebody, I wouldn't view it that way - you've spent a LOT of time familiarizing yourself with the music and the LP's to know that they're worth more. It will take you substantial time to clean up the collection, substantial time to sell the individual LP's you're not interested in, etc. All the while, the guy who sold them to you has his $500 hassle-free dollars.
If, before giving the guy the $500, you lined up a buyer for the collection (or knew you could have one) who would pay you $2000 for the 100 records, as-is, I would probably at least suggest to the current owner that he could get a pretty penny for his records and point him in the right direction. At that point, you've invested no time and you've done a good deed. Even there, I don't think you're morally obligated to approach it this way.
In any case, if the seller walks away with a smile on his face, has freed up storage space, and never has to think about it again, I think you've both made a good deal.
Say he has 100 records and you're going to give him $5/each, or $500. From his perspective, he just got $500 for something that was just taking up space for him, and with almost no effort.
From your perspective, you're getting a fantastic deal - again, coming into some great vinyl for a fraction of the market value. While this may seem like it's taking advantage of somebody, I wouldn't view it that way - you've spent a LOT of time familiarizing yourself with the music and the LP's to know that they're worth more. It will take you substantial time to clean up the collection, substantial time to sell the individual LP's you're not interested in, etc. All the while, the guy who sold them to you has his $500 hassle-free dollars.
If, before giving the guy the $500, you lined up a buyer for the collection (or knew you could have one) who would pay you $2000 for the 100 records, as-is, I would probably at least suggest to the current owner that he could get a pretty penny for his records and point him in the right direction. At that point, you've invested no time and you've done a good deed. Even there, I don't think you're morally obligated to approach it this way.
In any case, if the seller walks away with a smile on his face, has freed up storage space, and never has to think about it again, I think you've both made a good deal.