Re: Used equipment
You need to consider whether the electronics still function. Whether they are obsoleted by newer gear, whether there is any support or the maker has shut down. A VHF is a VHF, except, the new ones have DSC and if that matters to you, anything older has zero worth. Similarly, if there's a radar even three years old but you don't use or need radar, that's still worthless to you.
If you don't know what the instruments are or what they are worth to you? Better to buy a plain jane boat that doesn't have them, and add what you need after you figure that out.