I'm not too sure about this all. Yes, it can be a great opportunity, but I guess it's like fiat. Never loan on top of your abilities. If you have 4 Bitcoin, never take out a mortgage with 4 Bitcoin as your collateral, or you must be able to pay the mortgage in fiat any time.

I was searching for some more information after I wrote this blog, and actually found that if Bitcoin drops, you need to add more Bitcoin as a collateral or add fiat. So yeah, that's really something to be aware off before you take out a mortgage with your Bitcoin.