Signs that you can sell buy and do alot with them

I have used and seen plugins of signs that can be used to make stuff free or to dispose and stuff like sell buy trade.

I want this mod because not only is it good for making server shops, it can be very useful for people who want to make mini shops on e.g skyblock,factions and stuff like that.

And having sign shops are easier because having a menu, you have to create the item then make it so you cant lose it.

But with sing shops all you do is /shop or /warp shop and you buy stuff there.