Real money trading is against Warframe ToS.
You'll be taxed 500,000 credits per 1,000 platinum you buy from me. You will also need trash rivens/prime parts to fill up the slots in the trade
screen to avoid the platinum you buy being taken away from you. The suspicious trade detection system considers each riven/prime part to be worth around 833 platinum, so make sure you're able to give me the corresponding amount of trash rivens/prime parts (833x2 = 1666p, 833x3 = 2,499 and so on)
Of course, you also have to tell me your in-game name so that I can trade you the platinum. When we are in-game, make no mention of you buying platinum.
If you want to contact me directly for more information, add me on Discord @ Piccolo#1884