To build a robot base, we need the following:

• A good solid chassis with a good set of wheels with friction properties
• Powerful drives that can help carry the required payload
• Drive controls

In case you plan to build a real robot base, there are additional considerations you might need to look into, for instance, power management systems—to run the robot efficiently for as long as you wish—the necessary electrical and embedded characteristics, and mechanical power transmission systems. What can help you get there is building a robot in ROS. Why, exactly? You would be able to emulate (actually, simulate, but if you tweak some parameters and apply real-time constraints, you could definitely emulate) a real working robot, as in the following examples:

• Your chassis and wheels would be defined with physical properties in URDF.
• Your drives could be defined using Gazebo-ros plugins.
• Your drive controls could be defined using ros-controllers.

Hence, to build a custom robot, let's consider the specifications.