This is my Server shop section. It is a pair of command blocks with give commands and take commands, I also added a thank you message for the person when they buy something. The maintenance tunnels provide easy access to the command blocks so you can change the items and cost any time you wish. The commands can be modified as shown:

The thank you message command:

tell @p[lm=] Thank you @p[lm=] for your purchase!

The give item command:

give @p[lm=]

The take xp command:

xp -l @p[lm=]

Note: The xp is used as a currency so be fair with pricing.

.PLEASE comment problems or praise and if you want give a diamond thanks. I will be happy to answer any queries and am happy to help.

Additional Notes

You may think I am being lazy by just making one section but different people want to sell different items at different amounts for different prices so to get more shops all you have to do is paste a whole heap of them in a line. The design for the end that I came up with are in the photos. I have finished my work on the corner pieces so that you can have circular or bendy pathways of shops, they can be found here http://www.planetminecraft.com/project/shopsection-corner-piece/