The average salary in California is about $65,000, so this example could vary slightly.
Your friend makes roughly $5416 gross per month. Her house payment, without insurance & PMI, minus a $10,000 down payment would be, oh lets say $570,000 at 6% for 30 years.
That's $ 3,417.44 a month, plus probably $1000 per month in Taxes, Insurance, and PMI.
Now, when we convert $5416 gross to net, we have about $4300 per month we can actually spend.
She's already $117 per month in the hole, before cars, clothes, health insurance, or food comes into the picture.
Anytime a real estate market takes the median price of a home more than 2.5x the median annual income, it will not be able to sustain itself indefinitely and the price will have to adjust. When the prices fall into the crapper, that's the time to swoop in and buy. Some of these investors are going to be left holding the bag, but unless there is a major recession or depression, real estate works on a regional basis, so LA or Phoenix going to hell in a hand basket won't affect me much out here in the Midwest.