For comparison, we recently purchased a 1984 35-3. It had the engine replaced with a 2006 Yanmar 3ym20 a newer head sail, main sail age is uncertain, but it looks and sails ok. The electrical panels were replaced recently, a new stainless water tank was installed as well as a hot water heater, and a new windless. On the negative side, the boat sat for 3 years with a leaking anchor locker, minor leaks from the port, a leaking stuffing box, and a battery charger that has been charging at 16 volts and killing batteries. The deck sounded out OK, but I'm sure there are some issues in there. There are blisters, and I'm fairly convinced the keel bolts are weeping. The electronics were replaced in 2007, so not ancient, but old enough to be a bit buggy (radar, autopilot, and wind were not working at the survey, but the autopilot and Radar started working on the sail back to our home marina).
Most of the issues we knew about before the survey, but the keel bolts are a new find after the purchase process. The boat was originally listed for a little over $30k (I don't remember the actual price because I wasn't looking at the time). When the owner lowered it to $19k, I contacted the broker and asked for some more details and a chance to take a look. The boat looked good from the outside with an Awl gripped hull and rig. I told the broker I was interested and if I didn't make an offer, someone would soon. He said he's shown the boat 2 -3 times per week for 6 months, but hasn't received an offer. I told the broker I didn't want to offend the seller, but if I was going to make an offer it would be closer to $12k. He said they are willing to review any offer, but they would really like to get at least 10 after his $3k comission, so we offered $13.5 and they agreed. After seeing the stuffing box leak, we requested to have it fixed, they countered with $500 off and I was able to adjust it in 30 minutes after buying the correct size wrenches and soaking it with BP Blaster.
Was $13k a good deal? It's probably just about right considering the amount of work ahead, but it gives us a larger boat we can sail now and fix up along the way. A contributing factor may have been the owner's health and the marina it was in requires the year to be paid in full on January 1, we submitted our offer towards the end of December. This boat looks a little better off than ours, not sure what that's worth, but I hope this offers one more point of comparison. Good luck with the process!