A lemon grown from a pip will take some years to bear fruit. I have one that I planted 15+ years ago and although a nice size, no flowers and no fruit. Same with a grapefruit.

I would say don't expect fruit, if any turn up then you are lucky. I spoke to someone at the citrus centre once when visiting them and they reckoned 20 years for a pip grown lemon to bear if then . Could be a long wait.