Comment by cormorant

There's always some price at which an insurer would willingly insure. The only case where it is "impossible" is when there's a government price cap. The other issue that you implicitly refer to, though, is that the price of insurance can be altered annually, while the mortgage term is much longer. This mismatch creates "what happens when their collateral becomes [so expensive to insure that the homeowner would never have agreed to this mortgage deal on these terms upfront]?"