You want to get into commodities, but you aren't yet willing or able to pony up the $50,000 required for a managed account? Don't despair. But do be careful.

Public commodity funds offer minimum investment levels as low as $5,000 (sometimes $2,000 for individual retirement-accounts). Mostly sponsored by brokerage firms, the funds are registered with the Securities and Exchange Commission and with the Commodity Futures Trading Commission (CFTC) participants -- are sponsored both by brokerage houses and by commodity-pool operators (who are often trading advisers as well). Usually registered only with the CFTC, they typically offer initial investment levels from $10,000 to $50,000.

The track record of both kinds of funds, however, is less than stellar. Although they did well in 1979 and 1980, public funds gained only 3% a year on average during 1981 and 1982. By late fall 1983, they were losing an average 16% over the previous 12 months. Private pools were doing better, but many of them, too, were showing losses for 1983.

Why so lackluster? Professional commodities traders, after all, are supposed to be able to make money whether the markets are going up or down. One explanation points to the fact that funds run by brokerage houses make most of their money on commissions. They are unwilling to let their positions ride, the argument goes, and thus they undermirie their best chance for big gains. Another theory holds that successful funds quickly get too big, thereby running into legal limits on their holdings of individual commodities. That forces them into less-promising markets.

Bob Purtell, director of Merrill Lynch Futures Management Inc., has a simpler explanation for the funds' poor showing: He believes the industry's cost structure is simply too high for good performance. Management fees, incentive fees, and brokerage commissions, he says, frequently add up to a load of more than 20%. And since the load has to be paid before net returns are calculated, the bottom line suffers.

In any given period, to be sure, there are a few funds and pools that perform exceptionally well. To find the best, check the listings in a recent issue of Managed Account Reports (5513 Twin Knolls Rd., Columbia MD 21045) or Futures magazine (219 Parkade, Cedar Falls, IA 50613). Still, don't invest money that you can't afford to lose. Although funds offer protection against the multiple losses an individual investor can suffer (and although most liquidate their portfolios if equity falls to half its original level), one thing no commodity investment has ever been accused of being is too safe.