I did not buy shares in the company upfront. I accepted a 20% stake in exchange for my agreement to part with 50% of all future earnings and commissions that I normally would receive if I am being employed by the company as a regular staff.
You are absolutely correct on the due diligence part. I have not seen the company's P&L, balance sheet, or anything. I don't even know how much revenue came in last year.
At the very crux of the question is this. "Am I better off keeping all of the commissions and earnings for myself or better off giving up half of it for 20% of the company". If you answer that its better off to give up half of earnings in exchange for 20%, then you have to ask yourself why? Why is it better? By what means are you using to determine that this is better? Only you know your personal situation.
Its entirely possible that the 60% shareholder already has plans to hire a new staff for the exact job that you will do, and has already projected the future earnings and commissions that the new staff will earn. He might have thought that this was too expensive and came up with this scheme to roped you in for 20% of the company. Hence he has added 50% of your income to his bottom line, and he has control over what you can get out of the 20%. Good for him, not good for you.
On the other hand, if you are buying your job security for 20% of the company by giving up 50% of your earnings, is it worth it to you? If you worked for someone else, can you earn the same income? Will you have the same job stability? If not, then this is just an assured job position for a reduction in wages. But if this is the case, then you should have an employment agreement. Something along the line that if the company forces you to leave, then you get back X amount of the money you put in. In other words, you get your shareholders money out.
Because lets face it, you are actually doing cash injections into the company every month through giving them 50% of your pay. Its almost like an instalment plan where you are given 20% of the company up front for no money, but you pay for the 20% through your monthly 50% of your compensation. At some point, you should negotiate when this will stop. Otherwise, your financial contribution can surpass even all the other shareholders combined. eg. Lets say every month, you earn $20,000 in total compensation. You give $10,000 to the company as part of the 50% agreement that you have. If you work for 2 years, you would have injected $240,000 into the company. That makes the company's theoretical worth to be $1.2 million. Is this a $1.2 million company? How much did the other shareholders invest? If they started the company with only $150,000 of their own money, then you have put in $240,000, shouldn't you be the majority shareholder instead? Its better for you to have an agreement where you say you will give them 50% of yoir compensation for lets say 3 years, and after that, all 100% of the earnings belong to you. That way, you put a valuation on your 20% stake and on the value of the company. Or in another case, say you will put in 50% until you reach say $100,000, and then you stop. Otherwise, it does not look good.