That old pringle would be a good starter unit. Don't be a rotobrush hack
I just started my own Duct Cleaning biz after seeing a huge hole in the market where I'm from.
I'm going up against a couple of companies that currently use only Rotobrushes. When I pull up to the house in this:
for an estimate and explain how the system is going to be cleaned it's a no brainer for the customer. Only problem with CaddyVac is they are not cheap. The operation though is first class and I've received a lot of help from them. I figured if I wasn't going to go all they way I wasn't going to do it. I'm glad I did cause I love my Caddyvac!
The nice thing is that the market hasn't been ruined by low ballers like most carpet cleaning economies have. I.E. = carpet cleaning should be cheap.
I've had no problem getting prices like this: Base price 330 up to eight vents and $23 a vent after, 100 more for A/C and 100 on top of that if it is a crawl space furnace. I've been up and running for two months and my lowest priced job has been $522
The sad thing is that people have been paying prices like this for a rotobrush job.
Get yourself some education and look to cleaning to an industry standard.
http://www.nadca.com
Many have as many issues with NADCA as with
IICRC, but it is good to know what they are.
I'd much rather be cleaning carpet but there is such a hole in the market and so much money to be made I just couldn't pass it up.