If all you are going to tow is a pull behind mower deck, you should be OK with something like a Polaris Ranger midsize 800 .... or something in that range of towing capability.
The tow rating of rigs like the Ranger 800 is probably about 1200# or so. Most of the pull behinds such as a Swisher or DR brands will weigh I'd guess around 600#-750#. That's a fairly good tow capacity margin. Swisher's cost about $1800-$2000 and the DR's about $1000 more depending upon HP of the mower motor. For both machines you'd be looking in the $13K - $14K range minimum.