I setup cheap rentable storage at the start of the map but you can't really safely rent out parts of a chest. The way I built these units with 2 double chests of storage and LWC'd the door. I would add a user to the door for 50c a week and they would be the only person bar me that could open the door.
If the trade was announced and confirmed in the trade channel, that is illegal. Anything agreed on in that channel or on the forums in binding. If you then do not uphold your part of the deal by scamming, or killing the other member, that is illegal.
Minecraft ServerTrade Rules: 1) Do not post illegal trades or scams. 2) Do not sell items for someone else. Item(s) for sale must be in your possession. 3) Do not whore, or bash, for sale threads. If you don’t like the price, don’t post or PM the seller with your issue. Offers lower than the asking price should be kept to PM only. 4) If you find a post in violation, report it to the moderation staff. Don't take it upon yourself to confront the situation and escalate it past where it reasonably needs to go. 5) No excessive thread bumping, once every 2 days is sufficient 6) Only the seller is allowed to post SOLD in their f/s thread. 7) If you want to chat, do it elsewhere. 9) Do not list items for sale unless you are 100% positive that you wish to sell them -- no "testing the waters" to gauge buyer interest. 10) You may sale services rendered. You must, however, have a pre-determined cost for labor, etc. 11) Create your own threads. Do NOT post your items in another person's thread.