Ok guys, thanks for that info. The one he's looking at has the 0-470 engine but I think the prop has been converted to a standard oil driven one but I have no idea of what parts availability would be like for that engine.
The C35 originally had the E series engine rated at 205HP for 5 min then 185 continuous after that. The O-470 STC is a common one for the older airframes because it doesn't include the injection system. These engines came out of the K model, and some older Cessna 180/185s, and I think also the 336/337.
The prop will be a hydraulic CS prop, just like on most later Bonanzas and is generally reliable. Hartzell and Sensinich made props for the O-470 but it's pretty certain to be a Hartzell prop and governor on it.
The C35 airframe has heavier skins than the earlier planes. It also has the larger ruddervator, and should be fitted with the front edge cuffs that wrap around the ruddervator and are riveted to the fuselage. The C35 suffered from a slight decrease in overall performance due to it gaining some weight but the later model engine of 250HP can overcome some of the loss of speed.
Things to look for in older Bonanzas. Nose gear slop in bushings, gear, bearings, etc. Crazed, or dull plexi. mods that aren't approved, or have no 337 with them. Bonanzas are one of the most modded planes out there(like the O-470 engine mod). Drafty or poor fitting doors and sloppy hinges. Filiform(worm tracks) corrosion on flight controls. The orig control surfaces were Mag, and later ones were Al. You can tell which it has by the rivets in use, but I don't recall the signs on the rivet to figure out. Worn out retract/flap motors. The brushes are still avail, but some of the motors are getting pretty weak. Gear doors that don't close fully when retracted. Duct hoses that are rotted. Water damage from leaks under the carpet.
Bonanzas are pretty indestructable if maintained decently. Plenty have been deferred but one with a O-470 should be in good fettle. You'll have gobs of power on TO and it will tail waggle a little in turbulence, but they fly fantastic, and are quite the utility play for low cost. With the newer engine, no more auto gas STC.