The input terminals would draw what the internal LED current limiting resistor draws at the voltage you drive it at, minus the LED's voltage drop. I would think around 10ma at 5 volts would be a reasonable expectation. You could always just wire the input from the +5vdc and ground pins and measure the current draw with your digital multimeter. You do have a meter? all Arduino people need one!
BTW how much current does Arduino Draw from its outputs? Is it 40mA?
And Yes the SSR i am using has a Built in Resistor