"Insurance" organizations, who collect premiums for providing either life or property/casualty coverage, created their own types of loan agreements. "Banks" and "Insurance" organizations loan agreements and documentation standards evolved from their individual cultures and were governed by policies that somehow addressed each organizations liabilities (In the case of "banks," the liquidity needs of their depositors; in the case of insurance organizations, the liquidity needs associated with their expected "claims" payments).
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.
"Investment banks" create loan agreements that cater to the needs of the investors whose funds they attempt to attract; "investors" are always sophisticated and accredited organizations not subject to bank regulatory supervision and the need to cater to the public trust. Investment banking activities are supervised by the SEC and their main focus is on whether the correct or proper disclosures are made to the parties who provide the funds.
The final fourth sections contains standard text including details such as contract information, the relationships that exist between the finance parties - in the event of more than one tender and more than one law that apply to the agreement.
sample loan agreement between two people
loan agreement between individuals
loan agreement example