Old post, but,
Manaka san of the Jinenkan dojo was planning some time ago to begin an uchideshi program. So you may want to research that. However do not bother him with mild curiousity as you will destroy your own chances by doing so.
I would recommend you thoroughly research Bujinkan, Genbukam, Jinenkan and each of the ryuu that they teach within the organizations. Not technique collecting, but you need to find out what ninpo actually is before you decide to commit to something like that. From your post it sounds more like you're mildly curious rather than making an informed decision.
It's very likely your idea of ninpo is nothing like what the 3 organizations teach.