I'd say before you bought any dehus invest in some GOOD meters first and become proficient with them.
The world's best dehumidifier is absolutley useless without a well trained operator with quality metering equipment to find the moisture, quantify it, and track the drying process.
Before you invest in any equipment get some training and then work with another WDR contractor. Unlike carpet cleaning, you can not become skilled at WDR by takin a class and hitting the street. You MUST get experience from working with some one who knows. The nature of the work and liabilities do not lend themselves to learning on the fly.
It's not as easy as it seems and it requires a lot of dedication. It's not for everyone. I know a lot of guys who have dumped a lot of money into WDR only to find out it was not what they had envisioned.
Here are some key factors they you need just to start....
WTR & ASD.........................................................$3000.00 (tuition, travel, lodging, and meals)
CPL insurance.....................................................$10,000.00 to $25,000 year (several variables)
Meters.................................................................$1,500.00 to $2,000.00
Starter Equipment Package..................................$15,000 to $20,000.00
Marketing............................................................$$$$$$$$$$$$$$$$$$
Then consider that WDR must be a priority. If a call comes in it must be handled. That means that you will need to schedule less carpet cleaning to make time available for work that may or may not come in.
I'm not trying to discourage you, but I am trying to give you a gut check so you can be sure you want to do this.
Good Luck.
P.S. 200 HT hands down.