Renting of Immovable property

As per Section 22 of CGST Act , No it is not mandatory for your client to get Registration in Maharashtra where the property is situated. He can obtain Registration in Gujarat from where he makes Taxable Supply of Services & As per Section 12(3)of IGST Act , the Place of Supply related Immovable property will be where the property is situated , hence your client will raise bill to your Receptient by charging IGST . So even though the client is registered in Gujarat , IGST will be levy.

Note : But in this case the only disadvantages to your client is that any Inward Supply in relation to Immovable Property , the ITC on same will be not available to your client, the POS is property Situated , which is in Maharashtra & your client is registered in Gujarat.

So to avail any ITC in relation to inward supply related to property , your client need to obtain Registration in Maharashtra.