I think 'Go Solar' would be the best one to answer your question here. But to put it in a nutshell if you have a gravity fed water system then you can get by with a gravity or low pressure solar unit. In other words, if you have a tinaco or water tank on your roof and it is not a pressurized system then you can use a low pressure or gravity fed solar hot water unit. But if you have a pressurized water system then you need a solar unit that can handle the water pressure, and those are more expensive. I don't believe they are 4 times more expensive, more like twice as expensive. But either way in this sunny climate solar is the way to go.
I've used this site a couple of times in the past and I have been happy with their covers. http://www.solarcovers.com/ They give you good info on the different covers and possibilities and have quite an assortment and it's free shipping and handling. The problem is getting it down from the border as the covers are quite bulky.
My name is Tom Leonard, I saw your post this morning and I manage a couple of properties here so I know of some possibilities. Are you living in the area now? if so I could meet you and show you a couple of places. My phone number is (045) 333 142 0012.
Best Regards, Tom Leonard
PS I'm not a rental agent so there's no comission involved..