Question

why is Antonio unable to help bassanio at once???

Answer 1

Antonio helps Bassanio by borrowing money from Shylock, the Jewish money-lender, to loan to Bassanio so that he (Bassanio) can court Portia, a wealthy heiress.  Antonio's money is tied up in his ships and trading, so he doesn't have the cash on hand to loan to Bassanio himself.  The trouble occurs when Shylock wants a pound of Antonio's flesh, rather than the money paid back and the interest he would have made on the sum.

Answer 2

Antonio,the rich and prosperous merchant of Venice exclaimed to  Bassanio , his closest friend that he had no ready money available,since all his goods were on exportation and so after his ships would come home,he would be able to lend money to Bassanio. But since it was emergency,Antonio assured Bassanio by informing him that his reputation was good in Venice and so he would  borrow money from people in Venice.