A solid home security system should last you at least five years, so don't settle for cheap gear that quits after one season. Focus on weather-rated hardware that integrates with your existing smart home hub to avoid needing half a dozen different apps.
Tech companies usually refresh their camera lineups in the spring or late fall. If you can wait until a few weeks after a new launch, you can often find last year's perfectly capable model at a steep discount, saving you a chunk of that $500 target price.
The 0% intro window is a deadline, not a gift. If you still have a balance on the card after those 18 months, you will start paying interest on whatever remains, which can get expensive quickly.