I have found the same thing, it seems like no one has Villas or stadiums but that can't be right. I'm at level 30 and have several villas/cottages and one stadium (soon 3).
Should we make a list of of our progress on this challenge? How about:
Name. - (Level) - # cottage/villas. - # stadiums
Lilly2 (30). - 8 - 3