1) you've already been told to not even consider taking the money out of the 401(k) directly - that's a complete no-brainer. the "cost" of that money is extraordinarily high - you give up tax-preferenced savings that you can't get back (you'll never be able to re-contribute for the years you'd be taking back) and you pay a 10% penalty on top of regular taxes, so you'd probably have to have nearly $100k in your 401(k) to get the $50k that you want. that's some expensive money.
2) even a loan against your 401(k) for a home purchase makes little sense for most people. your retirement savings should be set aside and not touched, as FW indicates, unless it is an emergency.
3) this is an awful time to buy a house. please think hard about this potential purchase. even people paid by the real estate industry to promote home purchases, and people whose livelihood depends on a strong real estate market (like CEOs of home builders), are predicting declining home values during 2007.
if you insist on purchasing a home because you've bought into the realtor hype, please first spend a few days researching real estate trends, including recent stories in the wall street journal, and also a housing bubble blog or two such as
www.thehousingbubbleblog.com
, or one that is more local to you.
finally, ask yourself this question - if you, an individual who is responsible enough to have amassed at least $50k in his 401(k) at an apparently relatively young age, need to raid your retirement savings in order to be able to get your foot in the door, who is going to buy this home from you for a greater sum of money in the future? 2 years ago the mantra was "buy now or be priced out forever". now i'm reading realtors who can't make a sale saying "all the potential buyers have been priced out." exactly.