I think that I don't want to buy a brand new bike since this is going to be my second bike. (and if I fall in love with it I'll buy new). I think that my neighbor has a motorbecane road bike form the 70s or 80s that I can get for like $40 bucks, pretty good condition. Then I'll fix and upgrade it as I see fit.
But My main question is what do you need to have a hub that is coasting on one side and fixed on the other. Can some body post a link please. Also what else is required for converting a road bike to single speed. Obviously the front chainring/sprocket but I can just choose one of the ones that are on it now and match my rear cog with that.
Lastly what is a common gear ratio for singlespeeds/fixies?
Check the resource thread sticky. Read the info on sheldonbrown.com and then you'll be ready to ask some good questions and understand the answers. Hope that helps. Also, read the info on sheldon browns site that deals with french bikes, you may run into some of the issues dealing with old french whips.
the resource thread will help you for a lot more than just this one question... so by reading my answer you're obligated to read it-- but the easy answer is a flip-flip hub(one that's threaded for a fixed track cog on one side and a freewheel cog on the other like a bmx) on the rear wheel. with a conversion you'll need to make sure the chainline is straight which doesn't always work with road cranks.
if i were you i'd buy new... companies are offering some very diverse and great starter bikes with the boom in appeal.
or you could buy a new fixed gear and buy your neighbor's road bike and get the best of both worlds... but then again...