If you're selling something in a one-off transaction, you should try your best not to travel. There's exceptions -- plenty -- but most people are more willing to walk away if they haven't invested emotionally.
I just sold an office computer to a woman who wanted me to travel 70 minutes by rail to meet her, who'd negotiated quite hard and lengthily by email. I refused, and was ready to call it off. I knew once I got there, she'd probably lower her offer considerably.
A week later (yesterday), she traveled to see me, and only asked for 5% off, which was less than I was expecting and within the range I was already ready to do. If I'd traveled there, I could easily see her doing a "take it or leave it" at 20% lower than we'd negotiated, and leaving me having either wasted 3+ hours or taking less cash than was fair.
If it's a one-off sale with no relationship involved, try not to travel to meet the other side.