brands

Countertop equipent is usually lowered powered and designed for vendors, not large restaurants,  but in between the brands there's not all that much difference.

Griddles:......

Given the fact that a griddle is nothing more than a flat hunk of low-carbon steel, and that you live in Fla., and that the unit will be outdoors, I'm going to hazard a guess and tell you that you will have problems with rust.  The sucker's got to be greased like a pig when not in use.

Fuel. 

If you have nat.gas in your home, you can get a an outdoor conection for your equipment.  Alot easier and cheaper then messing around with propane tanks

Do you need heavy duty use or medium duty use?

You're asking about using equipment in a way it wasn't meant to be used.  Find something which suits your duty cycle and location.  Lots of heavy-duty, professional equipment won't function well for low use.  Some will.  You need to ask the vendors.

When you buy commercial, you want things which can be serviced and repaired quickly, inexpensively, and locally.  Check with local service people -- forget the vendors unless they also do repair and ask what they work on, and what they like recommend.  Warranty can be major also. 

You may need special, larger gas lines.  Ask the vendors about specific equipment.  Find someone to ask whether your local building codes will allow the right size lines and hook ups at your location. 

There may be other code issues and requirements, even outdoors.  I don't know, but you'll want to find out.

If your equipment is open pot and seldom used, simply use a lighter of some sort to light it each time you use it.  No biggie. 

Commercial griddles/flat-tops take a long time to come to an even temp.  They can't be rushed.   

BDL