My favorite type of student is one who wants to do intellectually stimulating things in the language and is not obsessed with accuracy. In my experience, they are more consistent people, maintain motivation and quickly see progress. The thing is, this involves working one on one, which I love, but it's not scalable. That's why I've targeted a niche where I see a clear need and where existing solutions are not optimal. I hope to validate (or not) the market soon.