In many major U.S. cities, it's becoming more costly than ever to purchase a home.

"Over the past decade, home prices in almost all major U.S. cities have increased," home investment company Unison points out in its newly released 2018 Home Affordability Report.

Large coastal cities have been hit the hardest. "Cities like San Francisco and Seattle have seen home price appreciation far outpace any historical precedent, growing as much as 10 percent year-over-year," the report says.

To illustrate what it takes to become a homeowner in various locations across the country, Unison calculated the salary needed to afford to buy.

To determine the necessary salary, the report looked at median property values in each area, then calculated approximate monthly costs for different sized down payments. For the purpose of the study, Unison assumed a 4.625 percent mortgage interest rate on a 30-year fixed-rate mortgage, property taxes of 1.25 percent per year and home insurance cost of 0.4 percent per year on the value of the home.

The resulting salaries assume homeowners aren't spending more than the recommended 30 percent of their income on housing.