They are the nouveaux riches of football but with very different business models: Manchester City and Monaco's Champions League last 16 clash on Tuesday is not one of equals.

Since being taken over by Emirati billionaire Sheikh Mansour in 2008, Manchester City have invested heavily in stars and played the international card to revive the fortunes of a club which has since won Premier League titles in 2012 and 2014.

The City Football Group oversees the activities of New York City and Melbourne City, and has shares in the Yokohama F-Marinos.

"City's business model is unique because of the City Football Group, which is different from what any other club is doing," says Rob Wilson, a football finance expert from Sheffield Hallan University.

"Relationships with other teams tend to be feeder club arrangements, but there's nothing on the scale that Man City have done.

"It enables them to exchange players at academy level, but as we saw with Man City and Patrick Vieira, they can also transfer coaches."

After two years coaching Manchester City's reserves, former France international Vieira was sent to take over the reins at New York City.

"It's like a global conglomerate in many ways," added Wilson.

"It's a unique selling point. Manchester United, Barcelona and Real Madrid have tours frequently to those parts of the world and have got themselves market position.

"So Man City are playing catch-up. That physical presence gives them something tangible to sell in each of those territories and gets people engaging with the sky blue of Manchester City."

Abu Dhabi cash has lifted Manchester City to the sixth richest club in the world, according to Deloitte's Football Money League, and the City brand is now ranked fourth in the world by Brand International.

Monaco, buy to resell

Bankrolled by Russian billionaire Dmitry Rybolovlev, Monaco had barely secured their return to Ligue 1 in 2013 when millions were poured into transfers.

Over 166 million euros ($176 million) were invested to bring in players such as Radamel Falcao (60 million euros), James Rodriguez (45m) and Joao Moutinho (25m).

Rybolovlev has succeeded in putting Monaco back on the European map with a return to Champions League football.

But Monaco have been caught by UEFA's Financial Fair Play regulations -- not to spend more than you earn -- and must sell on players at a profit in order to break even.

Rodriguez headed for Real Madrid for more than 85 million euros, a record sale for a French club.

Coach Leonardo Jardim accepts "the new project of the club" to promote brilliant talents in the Champions League and resell them at a high price, such as Geoffrey Kondogbia (Inter Milan), Anthony Martial (Manchester United), Layvin Kurzawa (Paris Saint-Germain) and Aymen Abdennour (Valencia).

"What we've had with FFP is a much closer alignment to financial sustainability," said Wilson.

"The key difference between City and Monaco is the broadcasting rights package available to City."

Wilson added: "The financial resources at Man City's disposal are much, much bigger than what's available at Monaco, so Monaco have to work much, much harder to generate those young players that they can either put in their first team or sell on at a significant profit.

"Monaco have been much quicker at adopting that academy-based model. Man City are doing the same. They're just doing it more slowly."

According to the head of Monaco's training centre Bertrand Reuzeau, "of a dozen players recruited aged 15 years in the centre, half will become professional -- one or two will integrate the professional group and three or four will finish elsewhere".

Last summer City spent 213 million euros on buying new players -- lead by John Stones (55m euros) and Leroy Sane (50m) -- eclipsing the 190 million euros spent the previous year.

By contrast, Monaco's spending was more modest with the arrivals of Djibril Sidibe (15 million euros), Benjamin Mendy (13m), Kamil Glik (11m) and Jorge (8.5m).

There are similarities between City and Monaco, but it's still not a level playing field amongst football's rich.