Add a minimum fixed fee + hourly after that. For example, you can say "I usually charge a minimum of 5K to solve these problems but it could bhe more depending

Add a minimum fixed fee + hourly after that. For example, you can say "I usually charge a minimum of 5K to solve these problems but it could bhe more depending on additional time spent" Up to 10 hours: fixed fee (.e.g $5K) 11 hour or beyond: $5K + $x/Hour Charge the min. amount upfront and then bill later for additional hours. Something like that can ensure that you are getting paid some minimum but are not going to lose money on large amount of work.