For first-time home buyers, closing costs are a major hurdle for home ownership. Coming up with a down payment and several thousand dollars for closing costs can be hard without home equity to tap. To help, buyers often ask sellers to cover all or some of these costs. In markets favoring buyers, this is a common habit, but when the market switches to favoring sellers it becomes harder. Sellers who know they may get multiple offers are less likely to say "yes" to this request. Yet even when the market favors sellers, buyers can still ask for this help. It…