I've gone to look at a small sailboat before & found that the title was obviously newer than the boat. On that boat, the HID number was not visible. I got the story about glass repairs on the transom having covered it. I got the story about the guy having bought it from an FWC officer (cop). I got the story about how he had only used it on a lake on private property & that's why it hadn't been registered in years. I didn't have the warm & fuzzys, so I passed on the opportunity. I'm not suggesting that this is the case with the boat that you are looking at. I'm just staring something that you might want to keep your eyes open for. These days, I always check the numbers on the paperwork against the numbers on the hull before going any further.
That being said, $500 for a daysailer is a great price. That one was registered in NH at some point & it has a motor mount. In my state, anything over 12' and anything with a motor needs to be registered. There is an exception for a motorless sailboat that is used only for racing. Different states have different rules about that. In some states, you don't need to register a motorless sailboat. I don't know what the local rules are where you live.
If it needs new sails, figure about $1,500. I see the mast. I see the boom. I don't see the rudder or tiller. You will need that.
The HIN number on most boats is on the upper portion of the transom, on the starboard side. That's the right side as you stand behind the boat & look towards the front. Any boat 1972 or newer should have a HIN number. Those daysailers go back to the 1950's, so the older ones might not have numbers on them. If the title says Oday on it, the born on date for the boat should not be past 1990, but if it's newer than that, it might have been built by another company that bought the molds from Oday when they went under. Failing companies often sell their hull molds. Companies like Can-AM Sailcraft, Rebel, Spindrift, Precision, and McLaughlin might have done something like that. I haven't looked at a daysailor in close to 10 years, so the details of the boat are not fresh in my mind.
I'd probably print the speck sheet for a daysailer & bring it with me for comparison. I'd bring a tape measure and a truck with a tow hitch on the back of it. The ball coupler is likely to be 2", but it could be 1-7/8", so I would bring both size balls. If the boat doesn't have serious mechanical problems, like a hole smashed into the bottom, or a cracked centerboard trunk, and if it's all there, and the paperwork is good, it would probably follow me home (says the guy who needs to sell at least one sailboat before buying another, because his fleet is too big)