Overweight guy doesn't want to be overweight anymore. Help!

I'm interested in buying a new or used road bike to help me get back in shape again. I need a reliable source of cardio and cycling works well for me. I am currently 230lbs and 5'11" so I have about 40-50 lbs I need to lose. I'm ok with spending more money if it's worth it.

Your level of experience with cycling Moderate. Years ago I rode in a couple triathlons just for fun. (I was more of a runner, swimmer than a cyclist.) A few years ago I made a big push to get in shape and was commuting to work about 20 miles a day.

What's your price range, and have you considered second hand? I'm thinking the lower end of $1000-$2000 range. I'm fine with second hand.

What's your intention with the bike - commuting, fitness, touring, sport, etc? First and foremost is fitness. I need to lose weight badly and I recently chip fractured my ankle so running is off the table for a while. I don't think biking will be a problem for me. If I can lose the weight again I'd like to make the jump into a cycling lifestyle. I want to ride regularly, maybe meet some other people who ride and just keep going and see where it takes me.

How far will you be riding, and how often? I'd like to ride pretty regularly for about an hour or so. I don't have any firm expectations here at this point.

Riding conditions: roads, pavement, trails, single-track, off-road? Flat or hilly? Traffic and weather. I live in Southern California so weather is usually pretty good. I'm looking at flat roads mostly with some hills.

Your location (even approximate) can help other locals familiar with your conditions, too. Southern California, Ventura County.