loan from a bank ... i want to know.. why will bank give loan and why wouldn't or someone is making someone else fool?

my neighbor called his friend. his new partner for business. they trying to open a new business, his friend said, bank does not give 100% loan. (*yes i know we have to keep "25% of asked loan as a guarantee and guarantee to pay back loan after credit is good) question is not this. question is: if there are 4 partners, each with 500k, can each get 500k loan with a down payment of 25% of loan amount for each individual.. (whenever credit gets approved) and not a question about guarantee. or bank can only give.. 25% of total business amount comparing... or all this is b***S****