I am a native English speaker and experienced copy editor. As such, I'm mainly bidding on this to highlight the fact that your budget is pretty low (at least assuming that your novel is the typical 80,000 -- 100,000 words in length). Even $250 only pays a first-world editor for around 2 days of work, meaning you will get a fairly limited cleanup of spelling and grammar. Larger issues (e.g. inconsistencies in descriptions from one chapter to the next, unintended stylistic shifts or significant plotholes) will be missed, as there simply won't be time to consider such matters. If you're on a tight budget, I appreciate that these may be luxuries you cannot afford, but I just wanted to write to you and help set your expectations as to what you will receive. Anyhow, good luck with your project!