Timeshares are a big business, withmore than 3 million US households payingan average of $13,500 for a week attheir dream vacation spot. If you want tobuy, don't think of it as an investment, nomatter what the timeshare salespersonsaysâ€”timeshare owners who sell in thesecondary market average only about50% of their purchase price. On the plusside, if you own a timeshare, you canswap your week for another in a differentlocale. But to avoid trading your treasurefor someone else's lemon, it's worth the$15 a year to join the Timeshare Owner'sGroup (www.tug2.net), which posts ratingson hundreds of resorts around theworld. Another resource for swappers isIntervalWorld (www.intervalworld.com),which will broker your timeshare trade.