Robots are for saving time, but a cheap one is just a loud paperweight. You want a unit that maps your home and actually scrubs floors so you do not have to touch it for years. Aim for a model with a self-emptying base so you only deal with the dustbin once a month.
Tech brands refresh their lineups every fall. We wait for October when companies clear out last year's flagship models to make room for new inventory. You get the same suction power and mop tech for hundreds less than the latest release.
Keep in mind that the 0% rate is a timer, not a gift. If you still have a balance after the 18 months are up, the standard interest rate will apply to whatever is left, making your vacuum much more expensive than you planned.