For towing 4-down, there are quite a few cars than it can be done. MORE than quite a few that CANNOT. Check your owners' manual. That should have any and all information.
Unless you have absolute confidence in a car salesmen, ignore them. All they want to do is sell the car and get their commission. I can't blame them, but it's up to you to RESEARCH! This forum has some good information as to where much of this information is.
If your vehicle should not be towed 4 down, there are a few things that can make it towable 4-down. All cost money. $1000 or so. A "driveshaft disconnect". A "transmission lube pump" just for two of them.
MY "toads" are: (used to be) a 1996 Ford Contour, speed stick. No mods whatsoever, put the tranny in neutral, leave the key in the ignition (keeps the steering wheels free) and simply; go.
Current "toads" are: 2007 Chevy HHR, automatic. Leave key in, put in "N" and pull a 2 amp fuse.
2011 Ford Ranger auto,4WD. Put it in "N", leave key in, buy a $400 Ford only "Transfer case neutral switch kit" (a rip...but.....) off y'go.
Lots of thought goes into a correct towed vehicle. G'luck!
A "Base Plate" for the "toad" itself....and a matching telescoping tow bar might run you 1200 bucks. Maybe more. Check "BlueOx". I have their product (base-plate) on both my "toads" and the same tow-bar (Roadmaster) with the BlueOx "knuckle" end....so I can use the same tow-bar for both.