"和已经卖掉而一年以上没有人入住的.." That shall have nothing to do with the bubbles mentioned. For instance, if those empty apts were bought and paid in full by owners without any mortgages. For whatever reasons the owners decide to hold them for several years with nobody living there(like three year CDs), so what? Even they had mortgage loans and as long as they pay the banks monthly payments, there should be no concerns to anyone.
The current subprime fiasco in the States could be an excellent mirror for China.
Even they had mortgage loans and as long as they pay the banks monthly payments, there should be no concerns to anyone. 
