My apologies for this relatively late response, but I would recommend looking into software like Blender if you wanted something free.
I know that if you do have the budget for it, you can certain look into Autodesk's software and other sculpting tools like ZBrush which may be relatively costly.
Unfortunately, I do not have experience in this field to provide much in the way of help, but I am aware that Blender does have a relatively open community for help and tutorials - but I personally found the workflow of 3D modelling to be a tad bit too foreign for me to grasp.
I'm actually currently learning 3D modelling and animation myself using Blender. I'm not comfortable enough rn to be doing commissions but when i get at least texturing and shading down, I'll come back to this thread and see what I can do