A solid mirrorless camera kit should last you five to seven years if you pick the right gear up front. Buying cheap starter gear usually means replacing it within a year, which ends up costing you twice as much.
Camera brands refresh their lineups every 18 to 24 months. That means last year's model drops in price right when holiday sales hit, giving you nearly identical performance for hundreds less.
Keep in mind that a 0% intro period is a hard deadline, not free money. If you still have a balance when the 15 months end, regular interest rates apply to whatever you still owe.