It'l work, I use water heater elements to heat my oil in drums. Make sure you have a port vented to atmosphere so the off gassing won't build pressure. ALL water heaters rather they are used for a week, or 2 decades WILL have calcium scale as well as other minerals built up as flakes in the bottom of the heater. It is hard to get them all out, but turning the tank upside down and flushing will help.
I'm on the lookout to find a short fat cabinet type 40 gal heater now.
Welcome to the board, and what part of TN are you from?