What is a procedure to operate his Mothers Business by son?

One of my client operating their transport business in his Mothers name. She is having many trucks for transportation. But his mother is old age. So he cant disturbs his mother again & again for any legal procedure like dealing with RTO, income tax, bank matters, or any other legal formalities. So what exactly he can do to make it business easy????

What is a procedure to operate his Mothers Business Legally??? which kind of Deed He need to make for legal works???