The claim that RSS is offering 500000 to Muslims first appeared after the "Agra religious conversions 2014" incident. Wikipedia says:
On 8 December 2014, Hindu nationalist groups affiliated to the Rashtriya Swayamsevak Sangh (RSS) were reported to have converted 250 Muslims to Hinduism in Agra. The incident was condemned by all the opposition parties. The functioning of the Indian Parliament was log-jammed in December. News reports indicated that Muslim right wing groups in India have received a `lease of life' in trying to protest the conversions. After a full investigation, the Uttar Pradesh Minorities Commission concluded that the Muslims had not converted as they continued to "remain Muslims."
The origin of this claim is Rajeswar Singh's open letter asking for monetary help.
Rajeswar Singh, the Aligarh area President of the Samiti, wrote an open letter asking for monetary help. He stated that the group had converted 40,000 Muslims and Christians in western Uttar Pradesh last year and started a target of 100,000 conversions for next year. He also stated that each activist who works to convert Muslims incurs an annual expenditure of 500,000 rupees and one that works to convert Christians requires 200,000 rupees. He sought monetary help from interested parties to run the programme of conversions.
But his claims are mostly untrue. Many of those whom he claimed has converted to Hinduism didn't actually convert. Some of them were misled to take part in hindu rituals. The wiki page says:
The Muslim residents of the Vednagar slum in Agra were told by a local Hindu activist that, under a development programme of the Narendra Modi government, if they attended a havan (a Hindu sacrificial ceremony), they would get ration cards and other basic amenities. Some 250 people attended the ceremony. When the ritual was over, the participants were told that they had all become Hindus.
Police then registered a FIR against those who misled Muslims to take part in a ceremony.
The Agra Police registered a First Information Report (FIR) against Dharam Jagaran Samiti and its convener in the State Nand Kishore Valmiki, and launched an investigation. Cases were registered under Section 153(A) (promoting enmity between different groups) and Section 415 (using fraudulent means) of the Indian Penal Code, based on a complaint made by one of the participants that was converted. The FIR states that ration cards and housing plots were promised for those who converted to Hinduism. Valmiki was subsequently arrested on 16 December.
But an investigation by UP government found no evidence of conversion.
The UP Minorities Commission that was probing the December 8, 2014 'ghar wapsi' incident in Agra -- in which 200 Muslims from a slum colony were 'converted' to Hinduism by an RSS affiliate -- has now said in its final report that no conversion had actually taken place on that day. The incident had triggered a national storm, with proceedings in both houses of Parliament disrupted for days over it.
According to wiki page cited above, another Hindu nationalist group announced their "biggest ever" conversion programme on Chrismas. They claimed that 5,000 Muslims and 1,000 Christians were said to be ready to get converted.
Another Hindu nationalist group, Hindu Jagaran Samiti, announced that it would hold the "biggest ever" conversion programme in the country in Aligarh on the day of Christmas. 5,000 Muslims and 1,000 Christians were said to be ready to get converted. Members of Parliament from Gorakhpur, Yogi Adityanath, and from Aligarh, Satish Gautam, have welcomed the announcement. Gautam declared in the Parliament, “We have been doing this (conversion) for several years and will do it again on 25th December. This is not a conversion but ‘ghar wapasi’ (home coming)." Vishva Hindu Parishad (World Hindu Council), one of the largest members of the Sangh Parivar, announced that it will hold a conversion programme in Rae Bareli, the constituency of the Congress party leader Sonia Gandhi, where it has acquired 60 families that are ready to convert to Hinduism.
That was also not true. Only 58 people were converted of which only one was Muslim.
