Hi,
I too work out in my bedroom and have to consider space, but I have never found kickboxing to cause me "space issues" so far. I have several different kickboxing videos and so far they have all been do-able in my "corner" of the bedroom.
How high impact it can get depends on what instructor you choose. My first kickboxing video was Kathy Smith's Kickboxing Workout, which was very informative as far as teaching the basics of punching/jab techniques and kicking techniques. I quickly outgrew it as far as intensity, but because the average advanced kickboxing video already assumes you have a background in kickboxing, or at least some prior knowledge of kicks/punches utilized, they often aren't very informative or "teach" to the beginner.
So here is my advice:
IF~you have $ to spend freely, then purchasing an informative beginner/intermediate type of kickboxing video like Kathy Smith's Kickboxing Workout would be a good idea, and safe way to learn kickboxing. Then you could move on to Cathe's Cardio Kicks (which can be easily modified until you reach her level of intensity/impact).
HOWEVER......
IF~money is an issue or you are on a budget (like me!), you could purchase Cathe's Cardio Kicks and just really preview it well, and take your time with the moves until you are sure you are performing them correctly. Cathe's video is intense, but the drills and basic choreography don't move as quickly as some advanced kickboxing videos. Cathe's is more of what I call "kickboxing hi/lo" and it was my first kickboxing video after Kathy Smith's, so I know that it is do-able for a person new to kickboxing. Cathe's drills will help you improve your form on kicks and punches as you progress.
Donna