HELP with *DARK* Live View in Manual Mode

Hey all, I am admittedly new to DSLRs, the D5100 is my first and I use it to photograph homes for real estate purposes. I shoot in manual mode, and prefer to use the live view to compose my shots, however in manual mode, the live view is incredibly dark, I mean pretty much black with only highlights showing (i.e. a sunny window). The way I photograph is to expose for ambient light, and then light the interior with speedlights, so aperture and ISO are pretty static, with shutter speed (based on ambient light) being my biggest variable in the exposure triangle. If I switch to another mode like Aperture the live view brightens up and I can get a decent live view preview. But in manual mode, it's maddening with the dark live view because:

A) focusing, even auto-focus, is really difficult

B) I have no idea what the shot looks like until image review

I'm really hoping this is a simple newbie problem with an answer that will be obvious in hindsight - I just hope there is a solution here period!

Thank you all for your time.

When you use live view on a Nikon, the camera follows the same steps as taking a picture. (Nikon uses mechanical internals to move the mirror.)

So since it uses the same sequence as taking a photo it is showing you the image stopped down to the aperture you are using. What lens/aperture are you using? Also if you change the aperture for some reason it still displays the original aperture you started LV with. To see the new aperture you need to leave LV and return with the aperture you want.

Also when you switch to A, the camera will adjust settings so you stay on the aperture. So the screen may brighten because ISO and shutter speed was changed by the camera for whatever aperture you set it to.

Your solution is part of your problem. You say that you expose for highlights and add flash for the interior part. Now just think about it for a second or two.
How long does the flash last? How do you think the camera's live view can show you what does not exist (no flash)?

So, you should be using the viewfinder to do your setup, cropping and then just review your shot on the monitor after you've shot with the flash and then correct accordingly. There is NO way you will be able to see what the flash will do in LiveView.

Enjoy your Nikon.

Hi all, just wanted to thank you so much for the input!