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 month

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.