After finally getting my car here, I topped off all the fluids, including the master brake cylinder which had an empty rear reservoir. Shortly after that we started noticing a drip under the drivers side dash, dripping down onto the car mat. It appears to be brake fluid. And now the rear reservoir is empty again. There does not appear to be any leaks from the master cylinder or the lines. Why would I have brake fluid leaking inside under the dash???

 

There is a seal from the master cylinder to the brake pedal plunger that goes inside of the car. That is the only logical place it could be leaking from, and it would explain why the rear reservoir was empty. That's where I would look first. It may be easier to remove the master cylinder and diagnose the problem from outside the car. Attached is a picture of the rear seal on both a power and non-power brake system. Hope this helps!