Background: I'm a twenty something male who takes guitar and foreign language from two private instructors. Both are master's level university students giving lessons as a source of side income. Both are around my age, one male and one female. I'm not interested in a romantic relationship with either of them. I've known both for about 3 months now meeting once a week for an hour lesson.
I think they are pretty interesting people and we tend to get along well. We also have a number of common interests (entrepreneurship software, arts, etc) and I think we would probably be friends if we met in another context.
Problem: Having the relationship of client to service provider gets in the way of interacting as individuals. Usually we'll only be able to have snatches of conversations before and after lessons, before they feel obligated to continue the lesson and give me my money's worth. I don't want to put them on the spot by asking them to hang out as they might feel pressured to do so to keep my business. Both of them seem to be tight on cash and have few other clients. I want to be especially careful with the female instructor since lessons take place just the two of us in her apartment. If she were to mistake a friendly invitation to meet-up as a date request, it stands a chance to permanently poison the relationship going forward. Does anyone have any tips about how to build a friendly relationship with either of these two people?