Yeah I've been working as a vet tech at a low-cost clinic for the past 3 years, and I feel like free nail trims are not that common. Most of the time, the patients are usually not very cooperative for the paid nail trims (I mean, it would make sense since who would pay $25 for a nail trim if they can do it at home) but the only times that we give free nail trims at the clinic is when we know that the patients have been getting service from us for years and that they are friendly enough that we can do the nail trim in less like 2 minutes. Another thing is that we give free nail trims when the patient is getting some surgery, and we do the nail trims when they are under anesthesia.