I bought a house outright when I was 18 that was £24,500. We lived in that until this year, when my mother decided she wanted to swap houses with us.
The house swap itself was a bit of a fiasco, I won't go into details, but anyway it worked out in the end.
We swapped with my mother, and got a remortgage so that we could give my mother some money (as her house was worth a lot more than ours).
So now, she is living in our old house which she owns outright (which is now worth around £120k), and she has some money to live off.
And we are living in her old house (which is worth around £300k) and we're paying off a £60k mortgage.
So we got a good deal I'd say!