Well, SK is not exactly free either, you can be jailed there for working with NK, but that's minor - SK is nearly in the state of war with NK, so I won't be judging them.
What is more important is that China has no choice in the reunification matter. Say, the regime falls. Is China going to invade NK and annex it as a province? No way. Is it going to set up a puppet government? No way, it won't last (they seldom do.)
Besides, why reunification would be a problem? This will neatly take care of the SK also, the SK will be too busy (and too financially committed) to do anything else, for many years. China will gladly let NK to bleed SK in the reunification mess.
With regard to the money, NK borders SK, China and Russia. These countries have more than enough resources to invest into NK. Of course there will be strings attached, like ownership of new factories, access to minerals, perhaps to ports, and so on. But money-wise, China is awash in money, in fact it *needs* to quietly dump some of the dollars it has. Rebuilding of NK will give a great pretext; depreciating dollars go in, land and factories go out. Great deal, I say.
Seems like.