looking to purchase a 5" GPS for my semi.....any suggestions which is best! Thanks

You can get a Magellan 1700 (7") from Tiger Direct for $100. You can upgrade it with Truck software for $150 after purchase. Half the price of one of the "Truck" GPS units. I have this unit and I love it.

Is there one that has live traffic updates that don't require a monthly fee?

I don't like the standalone units, so I use ALK's CoPilot Live Truck v8 for the laptop. It has traffic info for $9.99 per year, plus monthly map updates (free). I have a 7" touchscreen mounted on the dash which is hooked to my laptop in the sleeper.