If we take advance amount on rent shall we file gst nil return or non nil return?

On services (including rent), GST is payable on receipt or invoice, whichever is earlier. Hence, on advance GST is payable. 

In 3B it has to be shown as regular output tax. In GSTR1, it can be shown under advances and adjusted against invoice in subsequent month. 

Receipt voucher has to be raised upon receipt of advance. 

GST @ 18% would be applicable on the Advance Amount of Rent received. As per the Provision of Section 13 of the CGST Act 2017, the Time of Supply incase of Supply of Services is earlier of the following :

(a). Date of Payment
(b). Tax Invoice

Therefore you cannot file NIL Return for the month when you have received the advance payment...

Yes GST is applicable on advance received for supply of Services.