why is it not koupelny here?
You need genitive plural here.
Thank you! Is it because of kolik?
yes
Would it be wrong to word it like this: Kolik koupelen má ten dům?
No, provided you correct the *kolek -> kolik.
LOL. Sorry about that. Will do—thanks!
Just wondering why the verb is placed here. My inclination would be to put "koupelen" immediately after "Kolik".
Both orders are fine. There may be a very subtle difference in the preference for these two but that would require some difficult research. You can treat them as equivalent.