Vertical tank washers are not terribly space efficient. The footprint is small, but they have hoses sticking out. A 12x16 one is Big. You won't be able to/should not move it when full, and you must find space to store the thing when not in use.
When I was stuck for space, I used the bathroom, and washed my FB prints in the bath itself. Naturally this is somewhat inconvenient, as the bath must be very clean first, and no-one else can use it when your prints are washing. But one can get achieve washing as complete as by any other method. If this is an option for you, DM me for a photo of the DIY gadget that allows constant water flow without risk of flooding the apartment below!