Hourly rate will make more headaches for both of you. Fixed price allows you to negotiate up front, take a certain percentage as a deposit. Make sure IP is you

Hourly rate will make more headaches for both of you. Fixed price allows you to negotiate up front, take a certain percentage as a deposit. Make sure IP is yours till full payment is received. Changes in requirements should require a restructuring of the contract. Make the client work for being fickle. Get a statement of work. Clearly define requirements, again makes it easier for both of you. Never think in hours. Think in weeks. 3x your gut estimate should be accurate enough. Again: hourly is terrible. If your client is THAT focused on price you might end up in a bad situation where it's you vs them. That's a toxic relationship. It should be you two working together to solve a problem. Make this mutually beneficial. Lastly, never focus on savings. Focus on value add that your project will bring them. If this ML algorithm will help a core part of their business, make that clear to them. Your value add isn't an algorithm. It's going to help their profits by a measure of X%. Now some machine learning specific advice: Integrate what it might take to do data pre processing, cleaning and formatting in to your time estimate. Try to get as much information from the client as possible about the structure of the data, how they want it integrated etc. Oftentimes, I've always underestimated that part of the job.