It is all based on location, to you 600k may seem like a lot of money, which it is, but there is a vast amount of affluent individuals/families in this world. For example, the average income for my area is a little over $100k/yr.
If you don't have kids/major fiscal responsibilities, it isn't too hard to get approved for a loan that large. My buddy just bought a house for $450k and that is with a 65k/yr salary, no wife/kids and we are both 2 years out of school and make the same income.
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