I check out the complete camera and take it fully apart, bring it to the factory condition, test all functions, clean, renew, re-lubricate, and readjust the whole camera.
Also have a large supply of the NOS (new old stock) original parts and all related materials.
To check only for "one thing", for example, the compur shutter or the function of film advance, makes in the most cases absolutely no sense, because all functions in this camera depend on each other and due to the camera age only the complete re-build will guaranty the smooth and full operating condition. Sometimes I get some really new cameras in , where only general cleaning and readjustment must be done but it´s more like exception to the general practice.
In some cases I re-polish and re-coat lenses, mostly because nowadays vintage lenses on Rolleiflex suffers from problems with coating and lot of micro scratches, it´s extremely hard to find any Rolleiflex with a good lens.