Middleman Question

I have a question regarding RuneScape account upgrades. Since the sale of PINs is prohibited, I'm assuming the transfer of PINs is as well. Considering this, how exactly is a RS upgrade trade MM'd?

 

Example: 10m for RSPIN
Example: you seller and me buyer.
1) I give the MM/OMM 10m RSGP.
2) he confirms it.
3) you buy membership on my account and take a screen pic that you show the mm
4) i confirm and you get the money

thats atleast how i have done it with a MM from sythe. it was about a wow thing but it is the same deal ^^