there is NO BAD extensions
only some Extensions that are better than others.
.FM is NOT by a long shot the worst extension for that name
$xxx low as is
$xxx mid with mild developmentand promotion.
The keywords fit the TLD but I don't think it's easy to sell names in that extension. Plus, they are not that cheap. Are you prepared to renew in one year ?
Also verify the change of ownership procedures. I seem to remember somebody who was trying to sell a .fm, he needed to have documents notarized (big hassle).