Prior to entering into a loan agreement, the "borrower" first makes representations about his affairs surrounding his character, creditworthiness, cashflow, and any collateral that he may have available to pledge as security for a loan. These representations are taken into consideration and the lender then determines under what conditions (terms), if any, they are prepared to advance money.
It is an unsaid rule in the world of loans that one needs a co-signer to ensure that the student loan gets approved. That said, it does not mean that you would not get loans if you do not have a co-signer to sign on your agreement. There are some lenders in the market who would offer loans to you with you having to worry about the co-signer.
Loan agreements, like any contract, reflect an "offer," the "acceptance of the offer," "consideration," and can only involve situations that are "legal" (a term loan agreement involving heroin drug sales is not "legal"). Loan agreements are documented via their commitment letters, agreements that reflect the understandings reached between the involved parties, a promissory note, and a collateral agreement (such as a mortgage or a personal guarantee). Loan agreements offered by regulated banks are different from those that are offered by finance companies in that banks receive a "banking charter" granted as a privilege and involving the "public trust."
When you have a financial crisis, it is quite common that we search for various sources of funding. Though we might have helped our friends, they cannot do much when we are in need due to several reasons. If we maintain good credit score, then the best source for funding your needs is taking a loan that you can get through loan agreement process.