100-year mortgages are common in Sweden. A few years ago the government even had to pass a law to limit mortgage terms to 105 years, because banks had started selling 140-year loans.

It’s sort of a halfway house between renting and owning. As long as property values go up, both buyers and banks seem reasonably happy with the arrangement. Apparently the Swedish rental market is quite broken which led to this model, but I don’t know the details.

I also don't think top down land use regulation/zoning is appropriate. That's best left to localities with the exception of large projects (state and federal).

Why should Tokyo set zoning for Kagoshima?