The cheapest robovacs will only have a dock for charging. Pricier models incorporate self-emptying of the onboard dustbin, and draining/refilling of the onboard water tanks. The very fanciest models offer automatic mop pad cleaning, and detergent dispensing for the mopping fluid. Or if you're hunting for something even cheaper (in https://www.youtube.com/watch?v=Lhgk6D1ayeM&