How do you proceed when buying far from you house?

Hi, so tomorow I'm going to check my new boat ( a SAN of 2000) in north of England (about 4 hours by train) I have already gave a deposit.
Firstly is it some important stuff I should check on the boat ? Do you always try the boat on water?

If the boat seems nice I will buy it but how do you do generaly? do you trust the seller by sending him the money on his account before you got the boat? do you do half before and the other half once you got the boat?
The seller looks really nice and honest so if everything seems good I might send him the money on his account and then once he got the money I'll pick up the boat. but we never know...