It’s best, if you decide to hire a freelancer, to figure out what the going rate is for the service you need, and expect to pay that amount. Otherwise it may turn out to be a waste of money, because the quality of the service will suffer. Sometimes there are payment plans to help with high costs! But it’s really a good investment to pay industry standard for editorial services; I agree with Shayla.
Obviously there is a big difference. I actually started with screenplays (with some mild success) partly due to hearing that as long as you have a good story, the grammatical errors won’t be a big deal. Well, that was not true. Maybe if a producer liked the story or I was already established but every contest I entered always came back with feedback about the grammatical errors. Even if I won or placed as a finalist, I always received critique on that. Very little is spelling error, it was more about structure, etc.