Siblings agreement re properties

[mmljrr14]

I have acquired a property but still under my brother's company loan. I pay whatever is being deducted from his salary and all the other expenses for transfer. The loan is still on for 5 or so years. Also, my brother is married. The question is what is the document that I can execute indicating this setup? That I am the owner of the property and the legal documents saying so will be processed only after the full loan payment