Tax ramifications of adding brother to deed on house

I recently bought a house with my brother in CA, for loan purposes, the title was put into just my name. I have been looking at adding my brother to the deed as we are splitting all the payments 50/50.

If I do not add my brother to the deed, would I be responsible for paying income tax on the 50% of the mortgage payment my brother pays? Or is his payment considered a gift? Or are there no tax ramifications to that arrangement?

If I do add my brother to the deed, would this result in a gift tax for 50% of the property? Would this trigger any other immediate tax ramifications?