How is it possible to model a character (a face/a body) without ZBrush and on a tablet using only Autodesk Maya?

Answer 1

Polygonal modeling is the best way to start to keep things simple and to have a good foundation in your overall topology and edge flow.

Once you have a good foundation, you can use Maya's built-in Sculpting tools to start to sculpt higher resolution details. You can use a tablet with Maya's sculpting tools just fine as well.

Answer 2

Maya has a plethora of ways to model a character from scratch! Most would start with primitive shapes and modify those shapes into more complex objects by manipulating the underlying mesh structures (adding or removing detail as needed). Polygonal modeling is a great foundation to begin with!

As for your tablet, just make sure it meets the minimum system requirements set forth by Autodesk for the version of Maya that you would like to run.