1. 10% of income to be used on housing expenses
2. 10% of NW to be used to purchase a home to live in
That means that when you start the accumulation phase, to be in-line with the guideline is to just rent a room until one has a few hundred grand to buy a small house with cash? Either that or a house-hacking arrangement of some sort, right?
Mortgage companies calculate that you "should" spend about 28% of your gross income on housing expenses--mortgage payments, insurance, property taxes and condo or association fees. Personally, I've always thought that was stupid, since who has their gross to spend anyway? Why include money that you know you have to spend on social security, health insurance, etc. (Standard deductions from a regular paycheck).
So to really think about how to save money on housing, you can start there, and then think about reducing it. While you're earning money, maybe it makes sense to get a mortgage, but perhaps based on 20% of your NET salary. (So--say you make 50K a year, 28% of that would be $14,000, or $1166 a month. BUT.... if you use 20% of your NET, and let's assume your net after all deductions is around $40,000, so 20% of that would be $8000 or $666 a month. Then you get a roommate to pay for 3/4 of that and put it toward paying off your mortgage, along with what your regular payment would be--well, you'll have a paid off mortgage pretty quickly, mostly on someone else's dime.
To me, it makes sense to get your housing stuff squared away while you're still working, at least as much as possible.