Overly picky nit, Net 30 terms means you have 30 days after being invoiced to pay, it does not mean you get a bill every 30 days. If you order 10 different things on 10 different days, those invoices will be due on 10 different days.
It's entirely up to the company offering credit to determine what kind of due diligence they want to perform before giving another company terms.
If you're some random bozo I've never heard of asking me for quotes for 15K of toner im not going to send you anything unless you wire me money before delivery, more likely I just wont reply at all. (Used to get at least a dozen of these a week)
If you're an account I've been trying to sell into for months, and you finally agree to my meeting, me and the sales manager aren't gonna let the controller fuck this up for us, you can have pretty much whatever terms you ask for.