Power cords and brushes are typical electric tool repairs. Sometimes vintage tools suffer from gummed up grease in bushings and bearings or bad insulation on windings. Lubing bushings and bearings is no big deal, but if windings are shorted, they usually require more effort than the tool is worth to resurrect.
Remember, most electric tools are nothing more than an electric motor and a gearbox to convert the rotating motion of the motor to the desired action. Most non-worm drive saws don't even have a gearbox.
Most common problems I run into with older electrical tools are bad cords (easy fix) and bad switches (not hard, but a bit more involved). When repairing switches, challenge is usually having to find a way to repair or fabricate a replacement switch since new replacement parts are not available.