I tend not to think in % of salary, but what I am willing to part with. Of course this requires an insight in cost of living apart from rent, cost of utilities and how much you want to save up.
If you would be happy to life on $1500, save up another $1500 and have a salary of $15000, I take it you can rent considerably more up class. If an elaborate lifestyle is what you want, and saving up for a sabbatical or considerable down payment on property
, I would advise looking in the lower ends.
It's a matter of priorities, and what you have on a monthly basis.