You may be paralyzed because you fear your idea won't last all the way.
We have a tendency to "label" ideas as good or bad in our minds but that label has nothing to do with reality. So, our ideas must be tested in reality in order to determine if they are good or not.
So, just pick one and work on it.
If you get stuck, pick another and work on it.
Do you have a deadline? Otherwise just keep working on your ideas until you get stuck and do something to get unstuck. Perhaps writing on the third idea.
Sooner or later you will either realize an idea doesn't work, or have three novels.
There is no rule that says you must finish one novel before you can start another. Writing being such an organic activity just has to take the time it needs, and follow the paths it needs to follow.
For a community, you might want to look into NANOWRIMO. You're not really meeting people in the flesh, but they have twitter tags and possibly forums and it's one intense month (November) that a lot of people are doing the same thing (writing a novel). It might be the perfect thing to get you to write your first 50 000 words...
If you really want to, you could possibly find people to keep interacting with after NANOWRIMO ends.