Utilize open source projects (freshmeat.net). Stuff like the CMS Joomla and forum software like phpBB. You don't need a day job, so that's 18+ hours/day to teach yourself technical stuff.
If that $50k is tax free you have at least 1.5 years living expenses and enough cash to pay contractors on elance/craigslist to fill in the gaps.
My suggestion is that you get your hands dirty. See how much progress you can make. Be tricky: take short cuts, use open source software, use third party services, etc. If you're genuine and inventive in your effort I bet you can create at least a prototype. That's not just sketches on cocktail napkins, it's actual progress towards your goal.
The [how] of the concept is simple so I won't go into that until I have protected the IP or have developed trust in the individual. But I believe I have a way to inform people of [all] the upcoming events that they {the individual} is interested in but did not even know where happening.
Think of the application as your most popular friend in high school - the guy/girl that just knew everything that was going on. The guy/girl you would call to ask "what are you up to tonight?" "what else is going on?" And they could tell you all the fun things that were happening and what your other friends were planning on doing.
I believe I have a way to provide a more complete version of your most popular friend to the world.
I could not go into the other value proposition or sources of revenue without giving away the concept.
I greatly appreciate everyones advice. The YC community is an amazing place.