Booking a bouncy castle for a kid's party comes down to timing. The best local rental crews fill their weekend schedules early, so you want to reserve your setup at least two weeks before the big day.
A solid commercial unit usually costs about $350 for the afternoon. If you would rather keep that cash in your checking account right now, you can break the bill down into small monthly payments over time.
The 18-month window is a strict deadline, not free money. If you still carry a balance when those 18 months end, the standard variable interest rate kicks in on whatever is left, so set up autopay for $20 a month to clear it early.