I have bought lots like this before. You can actually do pretty well if the guy just wants to get rid of it. I always start with an offer on the whole lot at between 35 and 45% of retail, but remember, some used, some old. You have to take that into account. It won't sell instantly, but you should be able to sell all the stuff you want to in about 15 to 30 days. The last estate I bought I had everything sold in 4 weeks. Basically, if you can get it at 45% of retail, you can make a couple bucks, pay for the planes you keep, and come out ok. If you get above 50%, its better to let him spend the time selling it all seperate and buy just the parts you want.

If he wants a quick sale of all of it, he can't expect much more. If he wants more, tell him to part it out himself and he can do better.

Its not worth your risk to pay a lot and then have a chance of not getting your investment back out.