1) Assist in getting a loan 2) Assist in securing a loan 3) Back up a loan 4) Co-sign 5) Complete a lease jointly 6) Endorse for a loan 7) Formalise 8) Formalize 9) Help in securing a loan 10) Help to get a loan 11) Help to secure a loan 12) Help with a loan 13) Sign jointly 14) To agree with or endorse 
To sign jointly a promisoory note or any form of paper with another peson and share the responsibilty to pay the amount at the time of maturity.
To sign a document -- such as a promissory note or lease -- along with another person in order to share responsibility for the obligation.
[v] - sign and endorse (another person`s signature), as for a loan
co-sign verb sign and endorse (another person`s signature), as for a loan
to sign as a cosigner.