You can sell equity to anyone interested in buying it. Does your friends lower middle class uncle that retired from that factory job at Chrysler ten years ago have an extra 20 grand? You can sell him a chunk. You can't hold yourself out to the general public, but you can sell shares if that's what you want to do. There is a very real concept called cost of equity. It's a percentage comparable to loan interest. It's often much higher than the cost of taking a loan if your company is successful.
Equity in their business? You can create vtlynch LLC tomorrow if you wanted to and if you found someone to buy it, you could sell equity in it. What does that have to do with personal wealth?
That's exactly how I read it. Taking on debt or selling equity are some of the most common ways of financing businesses. I could see if "take on debt" was not in that sentence but even then many (non-VC funded too!) businesses sell ownership in their business to finance it.