This is a complicated question. Is it in saltwater year round? (Basically anything south of Jersey). The northern climate salt vessels have the same layup period that our boats do. Does the boat run into brackish or freshwater after its use? Is it flushed, washed and lift kept? Salt air will penetrate everything. You may chase wiring issues forever. Corrosion on all finishes. That being said you can find good boats in salt environments. My Tiara was in Cape Cod for 3 years. You can't tell it was in salt. It was well cared for and was only exposed for 3 years. The best advice I can give is have a thorough survey done by a qualified Marine Surveyor and be present when he does it.
Hope this helps.