That's how hedge funds work i.e.OPM. Billions of it. Before signing away your $ in their contract, read the very first disclaimer rule here. https://www.solomonhess.com/disclaimers-risk-disclosure/
There will be lot of prop offers that will give you better than 70-30 split (mine current one is 85%) but most will require you to put capital as they have first loss basis model. This is more so for firms outside the US but if you are a US resident then it is a diff ball game