Comment by aplummer
7 years ago
Hourly billing is how you protect yourself against a sloppy client like this, especially with unpredictability. I have seen fixed price blow up so much I would never ever do it personally - I would have to add so much it would be astonishing to be worth it.
I would never bid a fixed amount with a client like this. The only way to do a fixed-bid is if a) the requirements are 100% defined, b) appropriate controls are in place to account for scope changes and roadblocks, and c) the price of the overage risk were priced into the bid.
Firstly, I bet if you asked OP they would say $18k is "astonishing," and yet here we are.
Secondly, you can avoid most issues by charging for a weekly or monthly retainer. It's much easier to estimate number of months than number of hours.