WENZHOU, China — Chen Furong and his wife bought their home 23 years ago for its proximity to the city center and for the tree-lined canal just outside. Their dream was to pass it on to their children and grandchildren, a piece of wealth giving their family a share of China’s economic miracle.

Then their neighbor tried to sell her place — and it was all thrown into doubt.

Like every other homeowner in China, Mr. Chen and his neighbor own their homes but not the land underneath them. All land in China is owned by the government, which parcels it out to developers and homeowners through 20- to 70-year leases.

When the neighbor — whose surname is Wang — tried to sell her apartment, local officials told her that her lease on the land had expired. To sell her apartment, they told her, she would have to pay them one-third of the sales value.

Ms. Wang protested in a move that drew national attention. Suddenly millions of Chinese who had socked away billions — and possibly trillions — of dollars were worried as well. If the local authorities in other parts of China did the same thing, they thought, a big chunk of their own wealth could end up with the government as well.