Most homeowners would prefer to know where they're going to live before selling their current home. However, given current market conditions, you should buy before selling only if you can qualify to buy the new house and keep the older home should it not sell quickly.
Most homes sell if they are priced right for the market. But, to be on the safe side, be extremely conservative in estimating the probable sale price of your current home. And, factor in the possibility that it will take longer than you anticipate to sell.
An option for some sellers is to keep the current home as an investment. If you plan to take this approach, be sure to consult with your tax advisor regarding the tax consequences of converting a single-family residence to a rental property.
To avoid the risk of falling short of what you think your current home will sell for, consider selling it before you buy a new home. This may mean moving to an interim rental. If prices are soft in your area, the risk of losing out on home-price appreciation while you rent rather than own a home is slim. You might even get a better deal on the new home by waiting awhile before buying.Selling first and renting for awhile also removes the pressure of buying whatever might be available, which may or may not suit your long-term needs.