At the time of becoming the Prime Minister of our country one........

Indian Polity Union Executive

At the time of becoming the Prime Minister of our country one

Must be a member of one of the Houses of the Parliament. If not, must become a member of one of the Houses within Six months

Need not necessarily be a member of one of the Houses of Parliament but must get elected as a member of Lok Sabha within six months

Must be a member of one of the Houses of Parliament prior to appointment

Must be a member of Rajya Sabha

A prime minister must:

be a citizen of India.
be a member of the Lok Sabha or the Rajya Sabha. If the person chosen as the prime minister is neither a member of the Lok Sabha nor the Rajya Sabha at the time of selection, he or she must become a member of either of the houses within six months.
be above 25 years of age if he or she is a member of Lok Sabha or above 30 years of age if he or she is a member of the Rajya Sabha.
not hold any office of profit under the Government of India or the Government of any State or under any local or other authority subject to the control of any of the said Governments.