Have you considered the Soft Tub brand?
http://www.softubcanada.com/ca/home
They can be found used for $1500-$2000 and could probably be flipped for little to no loss if you decided you want to go to a typical hard spa or it is not for you. They are light enough that you could strap it to the roof of a minivan or SUV to take to a friend's house, cottage etc.
I have been bugging my wife for a couple of years now to put a Softub in our backyard.
Edit:
You could always move this into your garage if you wanted something somewhat indoors from time to time. They weigh less than 100 lbs when empty.
Also, brands to consider for a stereotypical spa include:
Hot Springs and their various brands
Artic (although their sales people and tactics have come under criticism and scrutiny)
Beach Comber
Jacuzzi (although my co-worker has had a nightmare with the one she bought a year ago)
Caldera
Have you considered the used route? My buddy in the G.T.A. got himself a large Artic one which would be $12000-$14000 before the install and electrical hook up. I think he paid $5000 or $6000 and he has had it for five years now with very few issues. There is a store in Cambridge that sells new hot tubs but they also sell a lot of used ones which include delivery and install and a 2 year warranty. Almost all of them are $7000 and under with many under $4500.