I highly doubt your proposed contract would be legally binding. I don't think you can sign away 1% of your total (pre-tax?) remaining life-time earnings. But even if you could, your prospective mentor is very likely to be ripped off. Let me explain.
I don't know how much time you want your mentor to spend on your development. But I'm assuming it is at least one month of full-time mentoring, so about 175 hours. From experience, I know that providing one hour of quality mentoring takes at least one hour of preparation. So the mentor would have to spend about 350 hours. The mentor wants to get compensated for this time. Since you want a highly qualified mentor and not just any random programmer, his or her hourly rate would be quite high. I'd say at least €60. So the mentor would be out about 350 * 60 = €21 000 before he or she starts making money of your salary.
The UK median salary is about €50 000 per year, but we'll assume you'll make €60 000 per year thanks to the great mentoring. Assuming you'll work for another 30 years that's a measly 600 * 30 = €18 000 into the mentors pocket (I realize salary increases makes this calculation suspect)
Clearly, the deal is not worthwhile. And that is not even taking into account the uncertainties (what if you die or get sick?) or that the mentor could have put the €21 000 in index funds instead, yielding about 3% per year or €50 000 over 30 years.
I have had a mentor. A guitar teacher. I paid him €40 per 45 minutes of mentoring. If I had told him that he could instead pay me for the privilege of mentoring and get 1% of profits of all my future record sales, he would have rightly laughed in my face. I don't understand why you can't do the same? If you have >$1M then you can surely afford to pay someone an hourly salary to mentor you?