You are going to Peru for the massive mountain vistas and the quiet mornings in the Andes. Booking mid-week flights keeps the base cost down closer to about $2400 before you even start looking at hotels and trail passes.
Spreading that total out over time makes the upfront hit a lot easier to stomach. We just need a clear plan to handle the math so you don't end up scrambling later.
That 0% intro window is a hard deadline, not free money, so if any balance is still left when those 18 months run out, standard interest kicks in on what you owe.