I did something similar, as a stupid teenager, once and it was honestly not worth it.
The request was to create a crypto trading bot for a specific market. No more details offered other than "a bot that trades crypto on market x". I said I was interested and wondered what their budget was.
It was of course 0 but since it would pay for itself I could share on the revenue, something like 20-30% for the first year. I replied a month later and said something along the lines of:
"Thanks for the offer, but I ended up just making the bot for myself and it has now made me a million dollars, at this rate I will have made over a billion dollars at the end of the year. This has totally changed my life, I am so grateful that you did not want to pay me for this as 100% of a billion dollars is more fun to have than a measly 30% . I just bought a freaking island!!!"
They then went ape shit and among other things made several accounts to try and get my account closed, I had to jump through all kinds of hoops trying to convince the platform that I had in fact not stolen anything and was in fact just trolling the clueless chump. Somehow that person convinced the platform to give them my details and several letters from lawyers arrived trying to pressure me into handing over the bot or paying millions of dollars in damages.
It was very stressful even though I knew that they had nothing and them being an American and me a European I just laughed in an accent. Though, after a bout a year or so of constant letters, emails, and online harassment I ended up sending them a very threatening cease and desist, based on some template i found online, pointing out that the idea "to create a crypto bot for market x" was public information since it was disclosed publicly and was not only the title but also the description of the task with no further information. I also mentioned that if they truly believe that I was now a billionaire then going after me without an actual case would be dumb since I could afford to keep them tied up in court. Never heard from them again but the damage had already been done.