* Some investors keen on direct foothold now

* Many eye companies already involved in Iran

* Others prepare for sanctions to be lifted

By Karin Strohecker, Daniel Bases and David Randall

LONDON/NEW YORK, July 20 (Reuters) - A few investors are racing to establish funds for Iran following last week's nuclear deal with world powers, and many others are tapping into multinationals already present in the $400 billion economy.

The agreement has made some seek a foothold in Tehran's $100 billion stock market even before sanctions are lifted, although others are taking a more cautious approach.

Classified as an upper-middle income country, with a population of 78 million and annual output higher than that of Thailand or the United Arab Emirates, Iran is set to be the biggest economy to rejoin the global trading and financial system since the break-up of the Soviet Union over 20 years ago.

Brokerage Renaissance Capital predicts $1 billion will flow into Iran in the first year after sanctions end, although that is not likely to happen for months and may not occur in one go.

London-based boutique First Frontier Capital Ltd. is in the process of setting up a sanctions-compliant fund dedicated to Iran, hoping to allow investors to take a position in Tehran's bourse before sanctions are lifted.

"This is a market where everyone is totally underweight and there will obviously be a lot of money going in, hot money at first but then also others," said First Frontier's co-CEO, Richard Adley, who plans to launch the fund in the next couple of months and aims to have 100 million euros invested by year-end.

"And then there is a big valuation gap there, Iran has a lot of catching up to do when you look at other frontier or emerging markets," said Adley, who estimates valuations at a very cheap five to six times earnings.

First Capital are not alone. In April, British-based Charlemagne announced it had teamed up with a Tehran-based firm, Turquoise Partners, to establish funds that will invest in Iranian securities.

Others, like MENA Capital CIO Khaled Abdel Majeed, are also getting ready to invest, but worry that a dedicated country fund carries too many risks at this point. Instead, Majeed is aiming to invest part of his firm's funds under management in Iranian shares - once the sanctions are lifted.

"At the moment it may be very marketable, but at some point it will become too expensive," he said, adding that the firm was starting its search for suitable local partners in Tehran.

"And there is also a lot of risk in the deal that has been agreed, and the regime itself is not stable enough to last another 50 years."

Both Renaissance Capital and the investment consultancy Ecstrat have reported a sharp pick-up in demand for Iran-related research from asset managers preparing to make the leap.

CHEAP VALUATIONS Some 780 million shares traded on the exchange on July 12, the latest data available on its website, representing about $64.2 million.

Iran mirrors Saudi Arabia in that both are diverse, geopolitically important markets with attractive demographics and stable populations, said Asha Mehta, portfolio manager at Acadian Asset Management in Boston who runs $500 million in frontier market assets for institutional investors.

Yet with issues of access and other trading logistics yet to be worked out for direct investments, international companies already doing business in Iran will stand to benefit, at least in the short-term until restrictions fall away, said Joana Arthur, equity product manager for London-based Ashmore, which has approximately $1.2 billion invested in frontier strategies.

Larry Seruma, portfolio manager of the $434 million Nile Global Frontier fund, said that he expects Iran will eventually become a "destination" for his fund. In the meantime, he is holding on to companies such as South African mobile network firm MTN Group Ltd MTNJ.J , which owns 49 percent of Irancell, Iran's second-largest mobile phone operator.

MTN Group told investors in April that it expected to repatriate about $1 billion in accumulated dividends and a loan repayment from its Iranian unit that had been frozen by international sanctions once a nuclear deal was finalised.

Multinational mobile phone companies, car makers and hospitality firms are seen as the most primed to benefit from the lifting of sanctions. ID:nL8N0ZK0GT

Bank of America Merrill Lynch said it sees Turkey and the United Arab Emirates as likely beneficiaries from Iranian foreign trade, which could increase to $200 billion by 2020 from $80 billion now.

Higher imports are likely going to come from the machinery, vehicle, iron, steel, food and consumer goods sectors, BAML said. Dubai's real estate and hospitality sector could also see an influx of Iranian cash and visitors.

Specific companies that could benefit in the short-to-medium term, highlighted by BAML, are Dubai real-estate company Emaar Properties EMAR.DU , Turkish oil refiner Tupras TUPRS.IS , Italian oil services company Saipem SPMI.MI , and Saudi Arabian food and packaging distribution company Savola Group 2050.SE .

Among automakers, Turkey's Tofas Turk Otomobil Fabrikasi TOASO.IS and Dogus Otomotiv DOAS.IS could get a boost, as well as French carmakers Renault RENA.PA and Peugeot PEUP.PA .

Iran's urgent need to upgrade its fleet of planes could bring a potential bonanza for Brazil's Embraer EMBR3.SA , Europe's Airbus AIR.PA and Boeing BA.N of the United States. 

Private equity firms will likely be another early mover, either taking direct ownership stakes in companies or providing financing to businesses looking to expand to take advantage of the young and well-educated populace. That will likely lead to more corporate bond offerings once the country is fully open to international investors, analysts say.

"Firms like ours are now starting to check under the hood. There are a lot of assets there that are going to need restructuring," said AJ Mediratta, co-president at emerging market debt specialist firm Greylock Capital Management in New York.

 ($1=25,535 Iranian rials)

(Additional reporting by Bozorgmehr Sharafed Nouri in Dubai and Sujata Rao in London; editing by Kevin Liffey and Philippa Fletcher) ((karin.strohecker@thomsonreuters.com; +442075427262; Reuters Messaging: karin.strohecker.reuters.com@reuters.net))