I owned a 351 for 5 years and there are some very good features and some issues to be concerned with. I loved the boats design and layout. In the mid 90's it was a very advanced layout and a boat that would surf in high winds easily exceeding her hull speed under thos conditions.
I will start with the issues to be concerned with:
1. If the boat has a Perkins M30 engine avoid the boat or replace the engine / transmission with a Yanmar. Reason is that this engine is really a lawn tractor engine that will not idle at a slow enough speed to engage the transmission without damaging the clutch in tranny. This is a big problem.
2. Early models have only 2 cockpit winches making it hard to solo sail. you will need to add 2 new primaries at the wheel is equipped as such & reroute jib sheets.
3. Mid 90's & earlier Beneteau's have a hull blister problem. If the hull has been peeled and re-gelcoated or better yet epoxied over all will be good. It's a percentage of these that have issues.
4. General advice on Beneteau's is buy one that was made in France. The quality is much better.
5. 351 boats are heavy in the stern and do not sit proper on the boats scribe line (heavy aft). Solution is difficult perhaps a different keel shifting some of the ballast forward to properly trim the boat.
6. The furling main on the early boats is tricky to use and can jam the sail in mast if not properly setup when installing the main sail, it can only be rigged oneway, the right way!
The good Side:
1. Great strong hull and rig. Well built and great interior.
2. Very usable fun boat to sail on.
3. Fun cockpit with a huge table and cooler.
4. Nice big Jib forward a 140% sail was standard.
5. Below decks two cabin layout was the best around and adding more house battery capacity was easy.
My final advice is to buy a 1996 or new 351 or 360 with a Yanmar engine and you will enjoy since they fixed most of the issues by then.