I am about to build a water surface vehicle (a kind of boat).

I was looking for different type motors and ruled out the stepper and servo motors. But I got confused between brushed and brushless dc motors. Brushless motors on one hand are more efficient but brushed are low cost and less complex.

Can you explain to me or get me some resource on how to find the best motor for low as well as for high budget? I am expecting the load to be around 12 kg. Please draw my attention to the necessary requirements that need to be keep in mind while choosing the motors. Also suggest me link where I can study about water thrusters and the propellers.