If your goal is to get some seed money, to build a "prototype" to raise money, then the net requirement isn't a full functional app, but just enough to get the point across in an elegant enough way to secure additional financing.
This could be as simple as a sketch on a napkin, and as complex as a full functional website with an e-commerce component.
As long as you can effectively deliver the experience of what it is you need money to build, then your medium for doing so isn't as important as getting the point across.
Looking around the industry lately it seems that you can't do a startup unless you're fresh out of college with not a care in the world.
On the other hand, if you actually have industry experience (even if you are under 30), you can't "drop out" of "real life" because of implicit responsibilities (socially - such as dependents, and financially - such as rent/bills).
Off the top of my head I think only 4 out of 36 startups in the current batch are fresh out of college.
Presumably YC only works for US companies, as people from outside the US (Canada, for example) wouldn't have the permission to work in the US for the three months?
The Vikings used to burn their boats so that they had to succeed!
Reads like you're already too comfortable where you are to take the plunge. If you can't work on your project part-time, then why not do some other part-time work, save the money and then Do It!.
Maybe you should think about what you could do if you only had 100.
Anyway, if you had the thing built you wouldn't need money, now would you?
If you need thousands to tens of thousands of dollars and have a rich uncle then the answer is probably yes.
If you need hundreds of thousands to millions of dollars and you want to raise from professional startup investors then the answer is probably no (Chris Sacca from Lowercase Capital says something like, "I invest in URLs not business plans").
There are exceptions of course.
Any longer project will be a challenge to finish because you'll lose motivation (for various reasons).
Launching quickly will give you a lot of insight on whether you are on the right track or not. And if you are, this will motivate you to start improving what you have built and probably rewrite it sometime later.
Shrink your idea.