Is nikon d3100 good in lowlight conditions?

Like night shots, dim lit indoor locations? I'm trying to start a photography business and need a camera that will work well for weddings and such.

I have a d7000 which is exceptional in low light.

The sensor on the d3100 is not the same, but i expect it would be able to handle low light pretty well.
I may get one as a backup body, myself.

You're "trying to start a photography business" but you don't know the answer to this? Lenses are more important than the camera body itself. An an 18-55 kit lens isn't gonig to cut it for weddings.

Use flash during weddings as much as possible but if it's really your style not to, get a camera with the highest ISO value you can find. More than the camera, you will need prime lenses, at least one normal/standard and one wide angle with the lowest f/number you can afford. With what you are trying to achieve, even f/1.8 would not be enough.

For light photos I use a Pentax K5 and it is exceptional

http://aviewfinderdarkly.com.au/2011/04/14/pentax-k-5-for-indoor-sports/

Nikon offer the same sensor in the D7000 and D5100

http://aviewfinderdarkly.com.au/2011/06/05/nikon-d5100-digital-slr/

The d3100, being the lowest end Nikon available, doesn't have the low-light capabilities to stand up to it's older brothers. If you are serious about "starting a business" then I would wait until you can afford a slightly better body. It doesn't have to be top of the line, but even with the best lenses, the d3100 will struggle in low light. I'm assuming that if all you're looking at is a D3100, then high-ticket lenses aren't going to be in the budget for you. Even if you had Nikon's best lenses, you are going to need some higher sensitivity to shoot handheld. As an experienced wedding photographer who shoots with Nikon, you might want to wait until you can get a better body. While flash is an important option, It can be difficult to use effectively at a wedding without much experience. Those who use them use them well because they have a lot of experience.

See for yourself

Yes it's great, and compared to the low light performance in beginner models a few years ago, it's excellent.

Here's a DSLR Buying Guide - http://www.the-dslr-photographer.com/2009/11/which-dslr-to-buy/