Renting home while divorce petition is pending

Yes, get a rent receipt from your brother and show that as a rental expense

however, court will be suspicious and may consider the fact that you gifted your flat to your mother.

so gift deed and rental receipts to be shown as evidence in the court of law.

Yes! you can.In addition to this you gather all evidence to prove in court that she has sufficient income of her own to maintain herself. But you need to pay all necessary expenditure of your son if he is in her custody.

The very concept of maintenance is that the petitioner is unable to maintain herself especially after having been forced to live separately from the spouse for whatever the reason may be;  now the question is whether she is able to maintain herself out of her sources of income, despite being a doctor if her income will not be sufficient enough for maintaining her life and status to a reasonable extent and that the spouse is earning sufficiently and more than her, then the court may order for an amount to be paid as maintenance to her.   Court will not be interested to probe into your personal affairs namely you gifting away your home to your mother and what she did with it after that and all that.  The court will analyse the facts put forth by both the parties before it and the fact that you are residing as tenant on a monthly rental basis will be considered while arriving at a decision over the maintenance petition.  Gather other evidences of your routine expenses too and produce them before court during the time of trial so that you may get the desired relief.