There is a reason why the FD lenses are lower in cost because it is hard to use it with the EF mount. It is mainly because of the different flange to focal plane distance(FFD) (the distance between the mount flange and the recording medium such as the film or sensor) between FD and EF mount.
Flange to focal plane distance of EF mount is 44mm while FD mount is 42mm. Because the FD mount has a shorter FFD, so in order for it to work properly, the end of the FD lens need to be inside the camera which is not possible. Even if you are able physically mount the FD lens on the EF mount, you are not able to focus to infinity. To solve this problem, you can get a adapter which has a lens inside the adapter to make it work. (which also act as a multiplier) However, the good one (one that does not degrade the image much) cost a lot of money to a point that it is not worth it.
However, Nikon F-mount FFD is 46.5mm which is longer than Canon EF mount. Therefore, you maybe able to use a old manual F-mount lens on a Canon EF mount camera with an adapter (pretty much the adapter is pushing the mount further away from the film/sensor) that do not need a lens inside. Personally I have not try that but search around the net may yield some results or examples.