A high-quality mesh system should keep your house connected for at least five years. Focus on systems that support the latest Wi-Fi standards so you do not have to replace the hardware when a new phone or laptop releases.
Wait for back-to-school sales in August to pick up last year's top-rated hardware. Newer models often offer minimal speed bumps, meaning you get the same reliable coverage for a fraction of the price.
Remember that the 0% window is a deadline, not free money. If you have any balance left after 18 months, the bank will start charging interest on what remains.