I am quite interested in an apartment in 30-yr leasehold. What will happen after 30-yr? no longer owned by the landlord? return to government? how to count 30-yr?

Many prior discussion threads on 30 yr leasehold issue - have a play with the search facility (top right this page) to find some of them.

Tip: click advanced search and then tick the box marked "search thread titles only" to narrow things down a bit. Most threads will be in real estate forum but there may be some in 'general' forum also (and others). try using search words "30 year lease" "30 year leashold" or similar