i.e. "Slaves can be held from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to demand compensation. " http://en.wikipedia.org/wiki/Slavery
If you have a mortgage you can still refuse to work and just become homeless. Company men will not drag you kicking and screaming to your cubicle and force you back to you home in the evening to watch X-Factor until you vomit and pass out.
The real thing that leaves families impoverished and destroys them is when they have borrow half a million for a house to live in, only to find out that's only really worth about a quarter million a few years later during the economic crash, thus precluding them from actually selling it and moving somewhere that has an economy where they can work. That's principal, not interest.
If you have to make a mental association between your mortgage and institutionalized human suffering, maybe indentured servitude would be a better (but still ridiculous) fit.
In the US, personal bankruptcy is an option. But not all Western countries have this luxury. In Norway, for instance, personal bankruptcy basically amounts to entering a 5-year contract of indentured servitude (you by law have to earn as much as you can, and get to use only the smallest possible amount of it to feed and clothe yourself - the debtors take the rest).
I think the term exploitation would cover this?
Even if there is some form of semi-institutionalized gouging, it's still not slavery.
[0] https://en.wikipedia.org/wiki/Human_rights_in_the_United_Ara...
[1] https://en.wikipedia.org/wiki/Human_rights_in_Qatar#Immigran...
The point is, that the comparison is still bad.