The vita only allows one account linked to it at a time. It has always been like that and never going to change. Not to be mean but the very fact that you know so little about the vita means you should not take this deal (which is a scam honestly). The person knows you're not knowledgable about...
If you have a ps3 then you only have to wait until the games are back on the store. Provided you don't plan to update your vita when the next update comes out.
I grabbed king of pool even though I already bought Ben 10. Significantly less space in size for the games. Much better for my 4GB I'm specifically using for TN-V. My 32GB still going to be for the vita side.