Welcome to Sailnet, dude.
I have a C27. If you don't mind a pretty spartan existence - it's doable. But it's seriously tight. And there is nothing like a closet...just a small hanging locker and under-seat stowage. I would compare it to living in one of those tiny "Scamper" trailers you've seen around. It's really glorified camping.
One important item will be the stove (if you want to eat). Ours has an old alcohol stove that we won't use. At some point I'll replace it with a propane job.
Then there are the water lines. In boats this old, unless they've been cared for and used frequently - they can get really nasty. So, even if the sewage lines are in good shape, if you want sink water, etc. pay attention to that as well.
Also, ours did come with a waste tank which is located under the dinette seat.
Apart from that, I'd agree with Faster that heat is going to be a big deal. Let us know how it turns out.