When I bought my DR...
Viewed it. Rode it. Decided I would buy it then and there. Agreed to do EFT. Seller printed a very basic contract, which we both signed.
I EFT'd the from his place, and had proof of payment emailed to him. And while I did that he filled out the necessary paperwork for change of ownership.
If you have an iPad or something with a banking app, use that. Otherwise, if you feel you can trust this guy, ask if you may make use of his internet/computer for the EFT.
As a precaution, I changed passwords etc as soon as I got home.
Congrats and all the best!