Stay away from any Wal-Mart boots. Plan to spend $100, minumum. I'm a guy who spends 90% of his waking hours in work boots, so I can tell you from experience, never skimp on boots, particularly if you are a big guy.

Georgia Boot Company has a lot of decent offerings in the $100-$175 range. I've had a few pairs and they hold up well. Carhart also has some pretty decent boots as well.