Mr Cameron’s main income is from making speeches around the world which are arranged by the Washington Speakers Bureau.
A testimonial from the Futures Industry Association says the former prime minister makes an “impactful and timely” speech and has an “approachable demeanour”.
Last December Mr Cameron spoke at a conference in India for £200,000.
The month before he had been paid more than £120,000, which is the equivalent to £2,000 a minute or ten months’ pay as Prime Minister.
Mr Cameron said he wanted to remain as an MP for Witney initially, but he did not enjoy being a backbencher.
However, he is understood to have wanted to maintain the lifestyle he was accustomed to.
Having stood down from the Commons he is not required to declare all outside earnings.
In the ten months between leaving Treasury and standing down as an MP, George Osborne registered more than £1million for speeches, mostly arranged by the same bureau, and also £650,00 annual salary to advise the investment manager Blackrock.
Mr Cameron has taken two unpaid roles at charities, becoming president of Alzheimer’s Research UK and chairman of the patron’s board of the National Citizen Service, a development programme for teenagers.
He has also set up an office in central London, run by Lawrence Mann who was his private secretary as leader of the opposition and prime minister.
He has also offered advice to Theresa May, visiting her in Downing Street at least once.
But, he has told friends he still has an appetite at some point to do another “proper job”.
He is keen on the idea of becoming the next secretary-general of NATO, which has been suggested by some people.
Mr Cameron is also spending most of his time writing his autobiography which is expected to be released next year and he is said to have received more than £1million.
In April he was mocked for spending £25,00 on a shepherd’s hut for his garden.
Although the former premier is keen to take a big job on at some stage, he has said he is determined “not to do a Blair”.
A reference to criticism of Blair giving political advice to foreign governments.