As you can see in the screen below, vendor is offering me fire lance spell with one slot free.
http://i.imgur.com/KrEoGBH.jpg
After buying, spell module is unslotted. Also I noticed that its randomizing almost every time you open vendor window, sometimes its showing free slot, sometimes not. Some spells show even 2 slots free.
http://i.imgur.com/VvsbEnv.jpg
Starter energy ball have it, freshly bought fire lance dont.
