I may come into a large amount of money and need advice on how to handle it.

1) A trust is simply a way to own property or assets and direct what is done with it: the trust becomes the owner of the assets and can pay out, invest, etc. the money or other property as the trustee (essentially, the manager of the trust) wants, subject to the instructions in the documents creating the trust (the trustee must follow those instructions). A trust is not itself an investment vehicle and the trust does not pay out or build interest. The assets or money in the trust may earn interest if they are then invested by the trust into bonds, CDs, dividend-paying stocks, or other interest paying investments--but then again, money does not have to be in a trust to be invested in those things.
2) Yes, a trust does have a person who manages it (a trustee), but again, they do so subject to the written documents or instructions governing the trust. Until and unless you see the trust document(s), you have no idea how *this* trust works.
3) There is no legitimate reason for them to do things this way. A trust, as stated in 1), is not itself an investment--it doesn't itself generate an increase in principal or interest. Also as stated in 1), the trust owns the assets--even if the instructions in the trust indicate that certain payments are to be made to you from the trust, you are only getting those payments, not the rest of the property or money in the trust. Plus, why would *anyone* pay 20 years of wages upfront? You don't indicate what you earn, but say you get $40k per year--why would he take $800k of his money (or, if he is assuming that it will grow over time due to interest, still at least $250k - $500k, depending on the interest he is assuming) and put it out of his own control, into a trust for someone who, in our example, only earns $40k/year? Depending on the assumptions about interest, inflation, time value of money, etc. and how much he initially funds the trust, he is putting likely 6, 10, and up to 20 years of your pay into the trust upfront--why would anyone do that, instead of just paying you for your work?
Plus, right now you say the trust *would* be transferred to you--when? Right now, you have nothing, just a promise. And will you see the trust documents and have a chance for a lawyer to review them with you, to make sure you are getting what you think you are--or are you just expected to take his promise at face value?
I used to work for the Securities and Exchange Commission: one thing I learned there is that any deal that seems too good to be true, like having 20 years of your pay put aside for you in trust, or that you will be paid for even more than 20 years, almost certainly is in fact too good to be true--it's generally false. I also learned that wealthy individuals are (with a few exceptions, of course) wealthy because they don't give away their money or pay people more than they need to. Something seems very fishy about what you describe.