I suppose that all transactions are different and are case by case.
Most of the time, (after an agreed price is established, (including whatever shipping and transfer costs are involved,) the seller waits for the payment method to clear and then sends the item out. If the buyer "appears" to be of good standing sometimes the seller doesn't wait that long.
When buying things here I always email a picture of the check, bank draft or USPS money order depending what is requested, picture of the addressed envelope and the tracking number.
Do NOT send FedEx 2nd day. Prices are exorbitant and the item does NOT make it in 48 hrs. Unfortunately "someone" has to pay for it and it usually isn't the seller. Total waste of money. Trust me I know. A $550.00 item becomes a $700.00 item and that sucks.
This is a great place to buy/sell. Even mentioning a nice 5906TSW has already gotten lots of attention, myself included. Is it originally a rail free one?
Jim