I remember when we used to allow guides to be sold.
Literally within the first week, there were hundreds of disputes, that's not even an exaggeration.
95% of people who bought a guide of some-sort were unhappy.
And the sad part is, you can't tell the difference between someone who is genuinely unhappy with their purchase, and someone who is using the guides content but just wants their money back.
As for educational services, I believe that it will backfire in the majority of user's faces.
For example, if two people purchase an essay on the same subject, the writer is bound to make similar points in the essay, which may lead to an investigation into plagiarism and would ultimately 'fuck' anybody up who had used the service in the past and those planning to utilise it in the future.
On-top of the fact that the work standard could be poor and then this will just lead to ridiculous disputes.
I personally don't think the sale of anything education-related should be sold in that way.
If you cannot complete your own work because you're too lazy or incompetent, then you don't deserve the perks that come with perseverance.
Sorry to say, that I'm against the suggestion for these reasons.