(FORTUNE Magazine) – Life hasn't been easy for sponsors of real estate partnerships. Many funds were hurt badly when various real estate markets around the country collapsed in the face of overbuilding. Tax reform eliminated most of the tax benefits. It's no wonder that investors are holding back. Sales of real estate partnerships are expected to total about $5.5 billion this year, down from $7 billion last year and $8.5 billion in 1986. To regain investors' confidence, sponsors have begun offering deals that promise to keep you financially whole even if the partnership's real estate investments do poorly. Five such funds, listed in the table above, have appeared so far. If the Houston office tower your partnership buys stands vacant until the 21st century, the general partner promises to repay every cent of your original investment, including up-front fees. Most funds will even give you a specified minimum profit, ranging from 2% to 9%. If you think that sounds like a good deal, you have plenty of company. One of the partnerships has already sold out and demand for another has been so strong that its sponsors have had to double its size. But peace of mind has a price. All but one of the deals take a portion of your investment -- ranging from about 5% to 9% -- to pay a big insurer or some other deep-pocketed third party to back the guarantee. That's a nice chunk of money that could be working for you, and it comes on top of the substantial front-end loads listed above. Moreover, the likelihood of the partnership ever having to use the insurance is remote -- too remote, experts say, to make the insurance worthwhile. A study by Robert A. Stanger & Co., an investment research firm, concluded that in most of the deals the value of property would have to decline dramatically during the life of the partnership before the general partner would be forced to seek help from the insurer. That's because the general partner can also use rental income, in addition to the property's liquidation value, to fulfill the guarantee. Since all of these new funds invest only in high-quality properties, Stanger, other experts -- and even most of the sponsors -- agree that the possibility of a substantial decline in real estate prices during the life of the partnerships -- typically eight to ten years -- is negligible. Of course, the experts could be wrong -- as so many were in another market last October. Even if they are right, the ultimate issue for investors to consider about these partnerships, says Stephen Roulac, a San Francisco-based real estate adviser, is ''not insurance against loss but assurance of success.'' He urges that investors examine carefully the general partner's track record and experience in property acquisition and management. All of the general partners in the table above have been in business for at least ten years. The fund that promises most should disaster strike is ML/EQ Real Estate. For would-be investors, disappointment if not disaster has already struck. This joint venture of Merrill Lynch and Equitable Life is sold out, and at the moment the sponsors have no plans for a second fund. Here's what you missed: The fund guarantees a full return of your capital plus a cumulative annual return of at least 9 3/4%. The guarantee costs 5% of your investment. Inland Real Estate Growth II doesn't promise as much as the Merrill/ Equitable fund, but it still gets Stanger's highest marks. That's because Inland doesn't siphon any of the fund's assets to secure a third-party guarantee. Inland promises investors their original capital plus 2% annually over the life of the fund, and backs the guarantee itself. Two funds co-sponsored by Prudential-Bache Properties, Summit Insured Equity II and Fogelman Secured Equity, promise you a smidgen more than the Inland deal and charge handsomely for it. For a 5.65% fee, used to buy a policy with Continental Casualty, Summit promises to pay investors 125% of their original capital over ten years. Fogelman will pay investors 128% of their original capital. The fund uses a hefty 9.3% of your money to secure the guarantee with a letter of credit from Citicorp. The most recent of the funds offers the least. First Capital Insured Real Estate merely promises a return of original capital, with no minimum appreciation. Its fee is 4.6%.

CHART: NOT AVAILABLE CREDIT: NO CREDIT CAPTION: GUARANTEED! If buildings like this Inland Real Estate complex near Chicago never found a tenant, investors would get their money back. DESCRIPTION: Financial data for real estate investment trusts that guarantee repayment of investment.