You probably can't, because there must be a reason for it to have lost 90% of its value, and that reason probably has to do with the house somehow (I named a few examples, but there are more possibilities) losing its capability to "house" people, because after all, that is the only value proposition of a house - that capability literally gives it its value.

> You probably can't [live in a home that loses 90% of its value], because there must be a reason for it to have lost 90% of its value

I agree 90% is extreme. However, the nice thing about owning a home is that even if it loses value, more often than not, other homes will also lose their value.

Say you buy a 1 bedroom place for 500k, and 5 years later you have 2 children and need a 3 bedroom place, but your home lost value and is now only worth 400k. The good news is that the 3 bedroom place also probably lost value. So even though your home decreased 20% in dollar value, the 3-bedrooms also did too, so your house (as far as in-kind value) is worth the same.

In fact, in some cases you could go further and say it's good if your real-estate loses money. Suppose that you bought that 500k place, and had 100k left in your bank account afterwards. Now 5 years later the real-estate market sinks 20% and your home is worth 400k. Suppose you didn't invest your 100k and it's still all cash. When the housing market sinks 20%, your in-kind trade value plus your existing cash is actually worth more than if the real-estate market did the opposite.

For the above reasons, it's better to think about your primary residence as planting a flag in the area that you want to live rather than a financial investment.