When I rented it was anything from 100%+ (when a student) down to 15% (highest salary I earned while living at my dad's house).
50% just on rent sounds pretty crazy, but as I pointed out the last time I saw a thread like this, the amount a person is earning has a huge affect on the impact of this.
-Someone taking home £5000 a month spending 50% on rent is left with £2500 for other bills
-Someone taking home £500 a month spending 50% on rent is left with £250 for other bills
I know that's an extreme example but it does happen, a friend of mine living in Kensington spends nearly 50% of her income on rent yet she is still left with nearly my takehome pay before I've paid anything!