Is it permissible to deceive one's father to give him rent with a mortgage, knowing that the father asks for rent on the mortgage, which is forbidden?

If the garage is owned by you and you wish to mortgage it for a debt, then the rent of the leased garage is rightfully yours. This is because the mortgagor (owner of the mortgaged property) has the right to utilize the mortgaged property in any way that does not diminish its value, such as residing in it or leasing it out. This is the view of the Shafi'i school. The Hanafis, however, are of the opinion that neither the mortgagor nor the mortgagee may benefit from the mortgaged property except with the permission of the other. As for the Malikis, they hold that the revenues of the mortgaged property belong to the mortgagor. The mortgagee is not permitted to benefit from the mortgaged property if the mortgage is in exchange for a loan, and likewise, your father is not permitted to take rent in exchange for the mortgage.