I don't hear about nightmare housing situations where 20% of a country's homes sit vacant while nearly the same number of people are homeless.
No, you don't hear those... They do exist. I live in Luxembourg, which is -granted- a quite peculiar place to live. In the capital (which is small, by any reasonable standards), there are 2900 homes empty (source: Près de 2900 logements vides dans la capitale. Link is in French). I don't know how many homes there are in the city, but given a population of 80000, with an average of 3 people per home (wild guess), we're talking 11% vacant. People want to live there, but it's simply cost-prohibitive. Owners don't want to rent cheaper: they'd rather have their buildings vacant than getting less than the perceived market rate.
I'm well paid, so is my wife (she actually makes more than I do, if she would work full-time) and we did manage to buy ourself a small home. We need to work both, though, and we did get a significant financial aid from my parents. Alone would be impossible. This brings me to another example: the house we got, is newly built. Formerly a big house was on the terrain, which was split for three smaller houses. This particular big house, was built in the mid seventies, and had been vacant since 2000. We just moved in our house, so, that's over 10 years completely vacant. The reason? Nobody can afford these kind of houses any more, especially if they're require some restoration. I don't even live in the city, a house like mine in the city is unaffordable, even for people in my income class.
Personally, I have no idea how, let's say, a cashier married to a bus driver (which is surprisingly well paid!) can even subsist in our country. I know as per fact, that many people with lower wages, just leave the country. Sure, it's not all that hard to do, given the country is so small.
I'm pretty sure, you'll find situations like these in many locations with high real-estate prices: Paris, London, etc...