I used to live in Manchester as a student a while ago, but I think prices would have increased since then.
While the cost of living in Manchester is much less than in it is hard to say what salary you should aim for because this will depend on your experience and field of work. Accommodation will always be your biggest expense. If you want a 1 bedroom place in Manchester, you will be looking to pay around GBP 600 per month. If you are willing to share a house you can pay much less.
We are busy putting together a Manchester City Guide, so do check back on the site more information.