Dear Sir or Madam,

The debt will be expected to be paid all at once, yes, plus delay interests and or penalties. Maybe even the communities' lawyer and court agent.

Yes, their assets, namely their property, can be seized and auctioned off.

Please read my article on the matter:

Comunidad de Propietarios: Avoid Problems with Your Neighbours in Spain - 26th June 2009

Yours faithfully,
Raymundo LarraĆ*n Nesbitt