Always try to do at least one round of proofreading yourself after you’ve left your first draft for a few days/weeks.

When you approach a professional proofreader with a clean version of your draft, it’s likely that their costs will reflect this.

Yes, proofreading your novel is time-consuming, and if you prefer creating to editing, you will need to force yourself to focus.

My advice here would be to proofread in batches and timed slots, say, an hour a day or a chapter a day.

Trying to do it all in one day is a waste of time because your eyes and brain get tired, and you miss the errors or add words that aren’t there—clever things our brains, aren’t they?