I advise players for free, for there level, game, age,and health.
Not for my benefit, just knowledge sharing and tennis caring...it is just the right thing to do.
I also just try to raise there level playing awareness for healthy long lasting tennis.
Most recs are playing without a foundation, so lessons are also recommend. Not from me thou, which I don't do anymore.
It just advise from my perspective and years of experience, knowledge.
Bottom-line thou: it is there health and there game...