Opamp input resistance
Since the opamp has very little current flowing into it, it can in most cases be ignored. For an ideal opamp (you need to erase the TL081 the input bias current is zero. For a real op amp it is uA to fA and for most cases can be ignored. This is why we use op amps, to buffer impedance.

The supply would then see the load as 20k for the VinB. 

For VinA there are to cases to analyze, but the supply will see 20k. 
If you want to know how much max current will flow, then consider when vout is 0V

Side note:However for the VinA the impedance will not be buffered and the current will change with Vout, which is what happens with an inverting configuration. A non inverting configuration would not see the effects of VinA