If everyone paid their invoices on time, then managing cash flow would merely be difficult instead of nearly impossible. Your customer's inability or unwillingness to pay on time has a direct bearing on your ability to pay your suppliers on time. For new companies, whose cash positions are often tenuous, the consequences can be frustration, fear and the learning of new phone skills. The reason for the 90 days is that so many of this region's companies rely on the automobile companies to pay their bills. Evidently the Big-3 can be notoriously slow to pay bills.
Interest is deducted by the bank monthly.
Just be sure you have the discipline to pay down your balance when the money does come in. Or the length of the agreement may expire and the entire balance becomes due and payable. Nothing like being in debt to keep the motivation level high. Be prepared to provide your personal guarantee when you sign the bank papers. Since you have complete faith in your enterprise and your abilities, this should not bother you.