Can starter be fixed or have buy new one? If have to buy new one, where is cheapest place to buy?

If starter is bad, You probably can't hurt it much more. If you are mechanically inclined,
Dissassemble look at connections, brushes. Other test arelittle more complicated.
If you do dissamble, let me know what you find.
First verify power making it to starter(Bad Ignition Switch)
Any Safety devices, Neutral switch, ETC.

:cool: HOnda riding lawnmower is getting power to the starter, but starter isn't working.
Thanks

Parts are available for that starter. Very expensive starter.

Don