Taking on a commission :)

[Midgardsormr]

I respectfully disagree with Torstan. I think it's good to have limits explicitly spelled out in the contract—they can always be waived for a good client, but it's difficult to put the brakes on a bad one unless you have the contract to back you up. "Good fences make good neighbors," as they say.

On the topic of too-restrictive contracts, just because someone asks you to sign an NDA doesn't mean you have to sign it exactly as given. Read over every contract carefully; if there's something you object to, it's okay to negotiate a change. And if there's something you don't understand, definitely try to get it clarified before you sign. Remember that informal talks are not binding; the contract is. So if there's something in the paper you're given to sign that is different than what you had previously agreed upon, that's a signal that your client is still in negotiation mode.

Oh, and "business angel?" That's very poetic! I think the English would be either "investor" or "venture capitalist," if I understand your meaning, but I think if I ever have money to invest I'll call myself a business angel instead.

edit: The topic title is a little vague, by the way. Maybe "Advice on taking a commission" or something similar would be clearer that this is a how-to topic.