For accessories - if you buy one with the box that came with the 401's, it can be spendy. If you find a set without the box you can save about 75% of the cost. It takes the same accessories as the 403 and the 500, and often you'll find a full set for the 403 way, way cheaper than one listed for a 401. Only real difference is the 401 has a built in cam stack so you don't need cams for some of the stitches.
I'll look when I get home, someone just gave me a bunch of Singer stuff and I know I have an almost full set of cams and maybe the feet too. If so, you can have it for postage as I already have full sets for two 401A's, a 401G, a 403 and the 500 (and they all take the same- so I really don't need any extras of them!)