BlackThorny: Regarding the steam cards again, If I can't sell them due to limitations and trade them to a friend,
Will he be able to sell them on the market without issues? (Suppose he bought on steam within the time period and has that app and all?)
Will he be able to send me steam funds somehow (not necessarily immediately)?
In theory, yes, you give him the cards and he sells them, now let's say that he made 0.80€ with your cards, how will he pass that cash to you (as steam wallet money)?
There's a solution but you need to be aware of 2 things, you can sell him something via Steam market but:
a) You will lose some money in the process since Steam get's a percentage (let's say that you made 0.80€, you will have to sell your item for that price but you will only get .70€, Steam gets .10€);
b) You will have to sell an item from a Valve game (a gun skin from CSGO, weapon from TF2, etc), cards won't work because you can't select the seller.
Or, as Triock said, he can buy you something with the same value...