My own experience seems interesting in view of the posts so far. I believe when I started in the yoshinkan, I told my primary teacher that I wouldn't mind teaching some day if I got good enough (or something to that affect). The more I trained, the more I realized it would be harder than I thought to have a dojo of my own and teach.
Teaching an occational class in someone else's dojo is one thing; having your own dojo quite another. I no longer have any strong wish to have my own dojo. I am more than happy (at least at present) just to have a place where I can train. I think only the lack of a place where I could train happily would influence me to open a dojo now...