So you're in the median bracket and you get your first serious, solid paying job by ~24/25. It's reasonable that if you're diligent about savings every month, you could have $45k+ by yourself at 32-36 years of age, and I'm assuming some financial setbacks along the way. With a partner, it really shouldn't be a problem by those ages. To do it before 30, you'd need a good economic pairing of two people that already are near or above $85k by 30. All assuming you're not living in an expensive market of course. With the necessary caveat: having children before 28 or 30 considerably changes the equation (unless you have a larger income in the household to offset that additional cost), as can serious health problems and associated bills (depending on your job/career situation).
Down payments are neither, unless your parents/inlaws are feeling generous.
The average savings account balance in this country is far less than 45k. You are completely out of touch if you think the average family can simply pull that out of their asses.
The median full-time income is about $50,000 in the US. Emphasis that that is the median, not average.
Two household incomes is ~$85,000 or higher at median type wages (assuming a pairing of one full-time median, one lesser).
Home ownership is very much within reach at the median, so long as your income matches your market. You can't live in major US cities, earn the median, and ever hope to own a home.