Just spend $300 on something from BD with brakes, like the windsor timeline and be done with it. I don't know why everyone thinks you need to upgrade these things. They are perfectly good bikes and anything more expensive will be meaningless to a beginer. Anything more expensive is way beyond the point of diminishing returns. Converting a bike inevitably ends up being more expensive and will take longer to get you riding, unless you have access to tools, a bunch of spare parts, and bike building experience. Building a bike a la carte is best left to experienced riders...its worth it if you've done lots of riding and have a well-developed sense for what will work best for you, otherwise you'll just end up spending more money changing it later.
Get a cheap durable bike and start riding it. It will serve you well. Experiment with different gear ratios, handlebars, tire sizes, pedal systems, etc, develop some mechanical skills workimg on it and RIDE IT INTO THE GROUND. If you are still committed, then build you next bike a la carte, or hold out for that perfect vintage conversion frame.