Fixed Per-Word Rate
The price I quote you (after reviewing the sample you send me) is a fixed price and will not change at any time during or after the editing process. This price is based on a per-word rate (not hourly) and into consideration total word count, complexity, frequency of errors, etc.
Most non-fiction manuscripts are around $0.014 to $0.016 per word. That means 50,000 words would typically be between $700 to $800 ($0.014*50000=$700).
Coaching
If you are on a tight budget, I'm happy to do just a section of your book as instructional edit, which would point out reoccurring errors and include plenty of tips and guidance on how to self-edit (but if there's any way you can get a professional editor to look at it, whether it's me or someone else, you really should).
Payment
Payment is in advance* through PayPal or e-transfer (bank transfer; Interac e-transfer). To make or confirm a payment, or to request an invoice, please contact me at fivefiftyau@gmail.com.
*other arrangements, such as dividing the project into sections/instalments or paying only half up front, may be possible. Please ask me.