Yeah... so 4kW in lights, 1kW in other grow equip, leaving nothing for regular house tasks = 5kw constant draw. Say you want to run 18/6 or 24/0, that means you need to pull over double your draw to pack away during the dark which means you need ~12kW in panels which alone cost from $30k for static panels laying on the ground to $70k for tracks and that's not taking into account the assload of batteries for the night, and we're not talking about a standard bank or even a double bank. Of course the cost of labor and amount of labor also great vary between different locations.
I think it's an awesome idea if you have the money but it definitely takes considerable start up funds. But then every now and then you can get em installed for damn near free if the write offs stack the right way.
I think you should do it for cheap through your friend and make a thread on it. I'd subscribe.