Usually the payment of a commission to the brokerage is contingent upon finding a buyer for the real estate, the successful negotiation of a purchase contract between the buyer and seller, or the settlement of the transaction and the exchange of money between buyer and seller.
The transponder cost for each account type is the same. The SunPass Portable cost is $19.99 plus tax, plus a required $10.00 minimum initial balance. The SunPass Mini Sticker Transponder cost is $4.99 plus tax, plus a required $10.00 minimum initial balance.
SunPass now comes in two types (comparison PDF), the $25 SunPass Portable (with no credit and minimum $10 charge) and the $4.99 SunPass Mini (with $4.99 credit). Online forums have reports of people moving Mini to different vehicles, but Portable is a safer play when trying to avoid triggering rental car charges.