The best time to think about selling your house is before you buy it.

You might have fallen in love with it and be more than willing to overlook a house's flaws but, before you make an offer, look at those flaws through the eyes of a potential buyer five or ten years down the road when it is your turn to sell.

And sell you will. Unlike their parents who bought for the long-haul, most first time homebuyers today stay in a house for only five years. So doesn't it make sense to think ahead? If you are interested in a house that isn't flying off the market today, what makes you think that will change when you are ready to move?

A house with a limited market will, by definition, require a longer time to sell and will generally lag the local market in appreciation.

The most limiting factor on home marketability is location. Say it quickly three times and you have a real estate ad, but a bad location decreases the number of interested buyers for a house and location, surprise, is nearly impossible to change.

A number of factors make a location undesirable.

Zoning. This might be as obvious and straightforward as the factory across the street or something unexpected like the old repossessed mobile home that is suddenly dropped on the beautiful wooded lot next door and rented to a struggling nine member heavy metal band.

Noise. Some people, you apparently, don't mind noise but others are hypersensitive to it. Traffic noise, sirens summoning volunteers to the local fire station down the block, low flying aircraft heading for the near-by jetport, will all limit the marketability of your home.

Heavy traffic. This is not only a noise issue but also a safety and privacy issue. Families with young children will generally avoid, if they can, houses on busy streets out of fear of the chasing-the-ball-into-the-street problem. The exception here is antique or historical properties which are often on original and now busy streets and command automatic marketability because of their provenance.

General neighborhood deterioration. Neighborhoods with lots of vacant and/or boarded properties are not good places for a homebuyer. You don't know where they might be five years from now. Leave the pioneering and the risk to investors and rehabilitators.

Inaccessibility. This can be a long dirt driveway that frequently washes out or a dead end street accessed only across a major highway with no traffic controls.

Even smells can be problem. You may not notice the odor from the meat packing plant two blocks away or the paper mill across the river, but it can become a factor when you go to sell your house.

Houses themselves can also present marketing problems that you should be alert to when you purchase.

Lot size and orientation. If asked, most buyers will say they want a fair-sized level lot. A house with no lot or one that slopes heavily, especially side to side, will be a liability, all other factors being equal.

Home Size: Regardless of the square footage of the house, the configuration of rooms is important for resale value. While many a couple has raised five children in a one-bathroom house it is not generally recommended for family harmony and a minimum of 1-1/2 baths tops most buyers' wish list. Likewise, the market for one or two bedroom homes (not condos - different audience) is more limited than for three or more bedrooms.

Local or cultural factors. You may love Walter Gropius flat-roofed contemporaries, but the market for them is limited in the Midwest. Cultural preferences not to mention snow load make them a liability unless Gropius himself gifted them with historical significance. While basements simply do not exist in many parts of the country because of ledge or the water table, where they are common, you want to have one. A couple who purchased a nice slab ranch in a community where the predominant religion encouraged food storage as a form of survivalism had a devil of a time selling when they had to relocate.

Ask yourself (and your agent) what the market in your vicinity wants, and, if the house you are eyeing has been for sale for more than a few weeks figure out why it hasn't sold.

That said, some of the factors we listed above can present opportunities; location for example. Zoning might be changed through political activism though it seems a little extreme to bet on it, but an unsightly view, traffic or privacy issues might be addressed through creative screening - fences or landscaping - that will hide the road or the factory (or the nine drum thumping tenants next door) or buffer surface noise.

You probably can't get traffic signals installed at the end of the street but you can grade, pave, and add drainage to a problematic driveway. It's just a matter of money.

Is there room to squeeze in a half bath somewhere in the house? Tiny sinks and smaller toilets make even a closet a possible powder room.

What about home expansion? Do the location and the lot make an addition, even if just as a pre-sale investment, a reasonable solution to the two bedroom or no dining room problem?

Can creative landscaping - terracing for example - turn a tiny or a sloping yard into an asset?

None of this is to suggest that you walk away from a house that you might potentially love because it has one or two problems. Every house has problems but some are only problems for you - no tiny extra room for your sewing or art projects or a little farther away from your workplace than you had hoped. The trick is to identify flaws that will pretty universally be viewed as such, figure out if you can change or improve on them, and then base your buying decision accordingly.