Opening a Physcial therapy clinic (in network) with someone

Looking to open a clinic with a small company I began working with. Joined on promise of ownership opportunity. Company was 1.25 years old. I then led to get the companies first 2 full time PT hires. I create all of our process and procedures. Customized all of our EMR. Created our RTM billing and do the billing every month. We are now looking to buy in and the owner estimated 50k. Also I would be paying 60% of start up fee but for 20% of ownership. I would keep my wages and benefits as an employee. 6% off the top would be take for billing and RTM. I feel what I have contributed by joining (and by giving up 40k appx in what I would have had made at other company (which he knew about and said I would make up in 2-3 years)) and the fact that I'm putting out 60% off starting capital would entitle me to higher percentage or the option of a higher percentage. If he opened himself he'd have to pay a CD anyway