When the housing bubble hit the US we were ready to sell and move to a bigger home, but were priced out of the market. So, we remodeled and added an addition that doubled the size of our house. While buying more square footage in the form of a new house was overpriced, building new square footage onto an existing house cost the same as it always had, about $100 per square foot.
We now own a larger home, and compared to our mortgage payment, we could rent it out for at least double that amount!
My SIL, however, bought at the height of the bubble and when they needed to move to a larger house because of having kids, they owed more than the house was worth. So, they had no equity to use as a downpayment on a larger house. They had to save tens of thousands of dollars for the next half decade for a downpayment on a new house. The old house hasn't yet rented and they may lose it to foreclosure.
My point is that you need to educate yourself about finances, mortgages, etc. I obsessively gobbled that information up and even took a college class on personal finance. I bought my first house at age 21, renovated it and flipped it for a profit that was used on a downpayment on a larger home. If I hadn't made it a point to follow real estate trends, I may not have recognized the bubble for what it was and may have ended up upside down on a mortgage right now, like my SIL, who, BTW is very smart, but just never educated herself on real estate.
Education, education, education! And that is exactly what the WTS discourages.
They might be kicking themselves in their collective ass when rents continue to rise and renters can't afford to donate anymore.
Funny, though, how the elders in my parents' congregation all own their own homes and/or businesses. It seems this advice is for the poor sidelined peons in the congregation. Maybe it helps them feel better since they can't afford to buy a house anyway.