Does a co-signer's income help loan odds?

Right now I am a student working part-time so I don't have great income, although my credit is good. Banks around here like to see housing to be less than 40% of total monthly income. There is an amazing opportunity to buy a foreclosure in the town I have been looking in but it puts me very close to the 40% cap. Does a co-signer help as a sort of loop-hole?