What i was thinking about was writing a fantasy story and after that i was going to write a sci Fi story and i was going to kind of connect them them together. I was going to think of an ending in the end of my fantasy story to tie it to the sci fi story, do or don't
It wouldn't be a bad idea at all. A good example of this sort of being done is Warhammer Fantasy and Warhammer 40,000, well at least initially they were connected.
Each story needs to stand on its own. If they are good stories by themselves, the connection is a bonus for readers of both. Just don't assume that people will read both.
Don't create that bridge in the first novel you try to publish. If it can appear in a later novel, and not require the reader to read the other work, it's probably okay. Linking sci-fi and fantasy stories, could be problematic, though. You;ll have to be the judge as to how compatible they are.
Two of my favorite authors, Vonnegut and Robbins, seem to do this. Sometimes I can't possibly imagine how the different stories he's describing could be related, but in the end it all comes together. My favorite movies are this way, too- they show the interconnectedness of life and the ripple effect that runs through it. It's all in the execution, but it can be done.
The problem with fantasy and sci-fi is that both are so rich in lore. In order to mesh lore together, you have to do it convincingly. If you cannot convince the reader that it makes sense, it usually can make readers upset or frustrated. One example is when George Lucas tried to explain the Force as micro-organisms in Episode I, it make several of my Star Wars friends upset.
