i filled out an application for an apartment, but needed a co-signer in order to qualify. i got approved, went to go sign lease, manager said that the co-signer had to sign the lease also, manager mailed co-signer a guarantor agreement which co-signer never signed nor the lease. only i signed the lease, was given the keys to the apt. i never moved in and returned the keys within 4 days of signing the lease. i tried to work out an agreement with landlord but landlord told me that they were not going to work with me. did the rental agreement ever become legal being that they needed co-signer's signature?