The shape of the new American housing market  the post-bubble market  is starting to emerge. It is one that favors the young who never owned a house and the banks that have access to cheap deposits. It may be harshest on the two coasts, where both distress and a newfound lack of mobility may be on the increase.

The ideal home buyer now  in a reverse of what was true for years  is a renter who is not burdened with a house. Such a buyer will need a down payment from somewhere, and he or she will need enough income to meet the monthly payments for the foreseeable future, including any increase in adjustable rates that seems probable.

But not owning a home, which may be hard to sell, is a big plus.

A year ago, having a home that had appreciated in value meant that an owner could trade up to a more expensive home. Now it means that the homeowner cannot move until the old home is sold, and that is getting more difficult.

First, the seller has to find a buyer who can get a mortgage. Second, the price has to be high enough to pay off the old mortgage and leave enough cash for the down payment on a new home. Both were taken for granted a year ago. In many markets, neither is a sure thing now.