Absolutely not. You can borrow money for a house (and just about anything else while you're working) but you can't take a loan for retirement.

Also:

>I'm just thinking my rent money gains me absolutely nothing. Its a full net loss.

That's not true. It buys you housing.

>Whereas my 401k(all index funds) will return what like 10% at best per year over my lifetime?

Which adds up to a LOT of money by the time you retire.

>I'm spending 20k/year on rent, so why not just take the 401k hit but actually contribute to a mortgage instead of just pissing money away in rent?

Rent isn't just 'pissing money away' and houses have a lot of costs that will also feel like you get nothing for, like taxes, insurance, maintenance and repairs, etc, etc.