I am a flat rate lead tech on flat rate but have a 40 hour guarantee, I pretty much have three apprentices that I assist when they need but two of them require almost constant babysitting. it is absolutely annoying having to help someone else make money while you sit there making nothing, but if they can afford you at 45/hr they can afford a minimum wage of some kind (30-35 hours per week is usually what I hear of). I would tell them to pay you hourly for the first three months so you can build a relationship with the apprentice, then migrate to a hybrid pay plan of some sort if they require a change and/or have a way to log your hours when you are assisting the apprentice. When I went from mainline to Heavy Diagnostics/head tech my hours dropped tremendously but that's also due to the brand I work for and their pay scales.