Concerning apartment evictions and co-signers; what are the penalties.?

was wondering if anyone knows the workings of rental lease issues and could tell me what the penalties are for a co-signer (not a tenant) of a rental lease where the co-signer has paid 5 months out of 8 months rent and the tenant is being evicted. If the co-signer does not pay anymore rent are they also liable for eviction court costs, any repairs necessary and cleaning and if so and the co-signer doesn't pay how much does it affect the co-signers credit rating and for how long.