Ten borrowers offered nearly $12 billion in corporate bonds Monday, and others are expected to follow. Insiders said as much as $30 billion in issuance could hit the market this week. "In many ways, it's not a bad time to lock in debt if you're an issuer," said Lawrence Glazer, managing partner at Mayflower Advisors. "Borrowing costs are low while spreads are narrowing. And tremendous inflows remain on top of what are historically low Treasury yields."