Use a standard 3 foot tank which is 90cm long 45 cm high and 35cm wide.
The divider height should be 1/2 the height of the tank say 22cm (this will give a decent swimming area as well as height to leap etc).
The filter shouldnt cost much at all perhaps $25 with hoses you need etc.
The sunlight from a near by window should be sufficient (not direct sunlight as it will encourage algae)
As for heat I dont think they would need it,but there is no harm in reading up on the species you wish to keep.
if heating is necessary use a small aquarium heater in the water.