The FW are fun, classy little machines. Altho they only straight stitch, they also made attachments to do most anything that modern machines do. You can get an aux. buttonholer, zig-zagger, monogramer (rare), ruffler, wide angle hemmer, narrow hemmer, tucker, 1/4 foot...
You don't need any of the attachments to do the most beautiful straight stitch you'll ever see, tho! They are too much fun to carry to classes, etc. If you pay a lot (over say $100), make sure the case doesn't smell, it should have the most common attachments, the ruffler, the narrow and wide angle hemmer, the tucker, and maybe a buttonholer. If you want more you can always get them here or on ebay! Look for the book, tho again you can get copies online for free or it's included in Nancy Johnson-Sebro's book, the Perfect Portable, which I recommend. Ebay'ers also sell nicely bound reprints of the manual.
I would take some fabric with you and go sew, see if it does anything you can't live without. If you fall in love with it, maybe he'll give you a good price because you love it and he wants it to go to a good home, you never know.