Ships sell for 90% purchase price, so for cheaper ships it's not so impossible to return them if you don't like them.
Just make sure you strip the ship of all the modules you can, before you sell it, and only leave on it the worst e grade modules possible - even lower class ones if you can.
Selling modules on their own, gets you the full price you paid back, but any modules that are on the ship when you sell it will lose the same 10% the ship does when sold.
It all makes a difference early in the game if you plan on not hoarding