I like how this rule sounds, but am wondering whether you live in a high-cost area or not. Having two incomes at the level of the fast-food industry seems somewhat limiting, but this depends on where you live and how frugal you are.
In other comments I'm also noticing that having a mortgage is part of the need to stay in a high-paying job, so maybe renting can alleviate some of that pressure and be more flexible to adjust to live below your means?
Renting is pound-for-pound far more expensive than owning. We couldn't find an apartment we liked within our budget, so we bought a starter home instead. Owning also lets us recoup value when we sell. Buying an expensive house isn't something we want to do, so there's no need for us to pay $2500 a month for a McMansion with a quarter acre of golf course outside.
Come to Toronto and say that to my face. I'm going to laugh, and laugh, and...
This may very well be true for your scenario, so I'm not addressing that. I just want to poke at the myth that owning is always cheaper than renting. The real answer is: it depends on a lot of things.
There are costs associated with achieving a purchase (and later, a sale), there are costs associated with paying rent for extra cash (ie the mortgage), there are property taxes, and there are both time and money costs in maintenance work (that is obligatory for owners, a savings if you are renting).
If you move more often than once every 5 years, the math probably works out for it being cheaper to rent than to own. Committing to 5+ years decreases your flexibility to do things like: take higher-paying work, let go of real maintenance needs, move out of a bad neighborhood, etc.