CAC units... need answers from homeowners who have them...?

I have a farm ranch style house in Suffolk county NY, and I'm considering installing a CAC system. The unit is a Ruud (similar to Reem) 13 SEER on one zone... my questions are: If you have this unit, are you happy with it? How much are your electric bills each month? Is it really cost effective to have CAC vs. in wall units? I had asked the installer (a friend) if I could have two zones... as I'm renting the upstairs to a tenant, and don't want to have the whole house cooled at all times... he said it's best just to have one zone, and that I really wouldn't be wasting money cooling all of it vs. some rooms at a time. Any advice would be appreciated.
Forgot to mention... I don't plan on staying in this house more than 6-7 years... and am worried that the cost of installing it wouldn't be worth it. I'm getting it pretty cheap ($6500), but could probably buy 4 in wall units and run them 24/7 for the next 7 years and still not hit the $6500 mark. Any advice??

Answers:
Seems kind of high, I just got a rheem 3 ton 13 seer for 3400.00
When you install a central unit make sure you use 1 ton for every 500 sq. ft. of house Oh If it includes ducts then that is an excellent price, And Ruud is a good machine

Other answers:
  • is there any houses for rent?
  • Does anyone know where I can find out who sells ant chalk in my area?
  • yhis is my first vege garden could someone please help me out on what goes in a garden that is easy to plant?
  • what products are reccomended for orchid care & fertilizaton?
  • Where can I find red huckleberries in the Portland, Oregon area?
  • Can i print out a list of low income housing in my area, that gives me the information?
  • Who has cheaper moving boxes? Home Depot or UHaul?
  • Does anyone know of a great rat trap? We live in the middle of the corn field and have problems with rats.?
  • I obligation to attain rid of the mustard algae contained by the pool. Please Help Us!?