Although it's currently a great time to sell a house in many cities, the favorable market conditions are transforming and giving more power to buyers.

There are two data points that demonstrate this. The first is the supply of existing homes for sale. Although this number is hovering around its decade low, we've seen it tick up in the two most recent months -- or, more specifically, the two most recent months for which we have data.

If this trend gains momentum, it could swing the market dynamics in favor of homebuyers. This is because, as in any other market, the greater the supply of available homes, the lower the price.

On this note, the second data point concerns home prices. Consistent with a tight supply, we've seen prices increase by double digits on a year-over-year basis for 11 consecutive months. On a month-to-month basis, however, the ascent is stalling.

As Motley Fool contributor John Maxfield discusses in the following video, this leads him to conclude that prospective home sellers would be smart to get the ball rolling on the process sooner rather than later.