These rules are out of touch:
Normal living expenses cost the same whether you make $250K or $50K. You use the same amount of food, buy the same amount of clothing no matter your income. Car insurance costs no more, haircuts cost the same. Overall living expenses are just about the same.
Also, in my case if I owned a home 25% of the house payment/property tax bill would be covered by what I pay in taxes. So if I had a $4,000 house payment, $1,000 of that would not affect my take home pay as It would lower my tax burden.
Are you planning on a 15yr, 20yr, 30yr mortgage? When do you plan to sell your home? Are you a good candidate for an interest only loan? Do you plan on getting married soon, what is your combined income? Will you rent a room?
You need to talk with a professional before you decide what home you want to buy or you will end up in a nicer/crappier home because you chose your house/neighborhood/location prior to understanding what you can afford.