Allow sellers to set up a custom lease.

-- Seller offers monthly parking for $150/mo but $1,500 if bought for a full year.

-- Gameday seller sells for $100 but is willing to negotiate down to $60 for a few buyers.

In both cases, the seller should be able to send a custom offer to the buyer without needing to edit the price of their spot and revert after selling.

Potential implementation (for devs):

-- seller cannot self-approve, but a buyer can confirm they agree to this lease and click to submit a request w/ those terms

-- lease then acts a normal lease

-- seller can approve/reject, buyer can cancel request (as normal)

Improved chat can also be included in this functionality (view all of the sellers' spots in the thread).