A mesh system blanket covers your home in internet, ending dead zones for good. Buy a solid mid-range kit now and it will easily last you five years before you need an upgrade.
Tech companies release new versions every autumn. If you wait for mid-summer clearance sales, you can pick up last year's model for around $300, which is just as fast for most home internet plans.
That 18-month window is a deadline, not a gift. If you have a balance left when the time is up, the bank will start charging interest on the remaining amount immediately.