You can charge per hour, page, or even per word.
As far as exact numbers go, I’ve seen rates as low as 0.05/word and rates as high as $80/hour.
It’s important to know that many it’s common to see very low rates, especially on bidding sites.
You don’t have to accept every project that comes along. And being turned away because you want “too much” is normal.
More importantly, make sure that money, no matter how small, makes it to your pocket.