Suggestion: list all options before assigning a "Plan A/Plan B" ranking:

( )Pursue your own business plan and forget about YC

( )Get accepted by Y-C and start your business that way

( )Work for a YC Founder.

Each have pros and cons, and everyone's goals and cabilities are a little different. Assign Plan "A/B/C" in whatever way works for you. For some, working for a startup company will probably be the best experience they can get if the goal is to start their own eventually.

Not all ideas, no matter how world-changing, can be turned into a full company with just one founder and roughly zero cash. For young founders, 15k, partners and a basic support system can make a world of a difference.

edit: The real deciding factor for me though will be his equity equation.

Right, but it's usually possible to find another, simpler idea - even if it's just consulting - that will generate $15k and bring you in contact with potential cofounders or customers.