Stefan, hi! you can probably get a room with some other folks. . . or if you're really committed, head to Seoul this weekend and get some cheap (but decent) camping gear. . . it may still be a bit cold this weekend, but with the weather getting better and better, you can get your money's worth. Might even ask around. . . your friends and colleagues might have tents and sleeping bags-- camping is popular enough here.
I think I posted a link to some hotels and minbaks in the park. The Youth Hostel also has rooms for rent and is pretty close to the campgrounds. Friendly and helpful staff if not really speaking English. The Seonunsan Tourist Hotel, is I believe the near-by hotel. . . with the sauna and near the norae-bang. Think last time the rooms were about W40k and probably still off-season, but don't rely on that 100%.
Sununsan Youth Hostel: 063)561-3333, 561-3448
Sununsan Tourist Hotel: 063)561-3377, 561-4700
there are climbers in Wonjuwe haven't heard from them about the meet and greet . . . to seonunsan it's a bit of a haul. How early can you start out? Check this thread
hnb-- while I don't know many people who lend extra ropes, you're sure to find someone who'll share-- I think that's pretty much everyone, Koreans included. I'll have a 70 meter, so two people could climb adjacent climbs on either end!