Leveraging retirement funds to start investing

[Ross Yeager]

I am 28 with a substantial income through my software engineering day job.  Over the past couple of years, I have accrued a substantial amount of cash in my retirement funds (401k and Roth 401k).  This has made up a majority of my savings (1/3 normal savings, 2/3 retirement funds).  I have been reading about ups/downs of taking out a loan against my retirement fund, and curious as to what the community has to say about this.  In retrospect, with my income stream and entrepreneurial spirit I wish I did not have so much locked up in retirement so that I could be using it to dive into some real estate investment (targeting multi-family duplex).  Any advice here?