Hello,
How important are illustrations to content in this market (plumbers/HVAC)?
I have a background in this area and have taught myself how to illustrate as well. Most topics are complex and difficult to communicate clearly to the layperson. As such I have been creating some illustrations that a writer could use to add some pizzzaz to their articles.
I am not selling any writing services, just illustrations.
Is there a market for this type of resource? ie. illustrations
Thanks for any advice.
Well, look at sites like stockphoto or 123rf or dreamstime… they don’t only sell photos, they also sell illustrations.
An image is worth more than a thousand words… a good illustration, too. 
It sounds like a very specific market to me to make illustrations for speculatively. Could you make a site or a blog where you showcase your images? I think this would make you more visible, you then work on any contacts you may obtain.
I’d start by doing some basic illustrations that someone might search for to get the visitors in.
For instance I have a content site where I have made some of my own graphics and illustrations, nothing fancy and some of them are just graphs I’ve made in Excel. I’ve sold their use many times for textbooks and even exam papers and that’s without me making any effort to do that. In fact I’ve reminded myself that it’s something I need to do more of.
I don’t think plumbers or HVAC suppliers surf the internet all day for cool diagrams.
Seems like you need a more direct approach.
Maybe find a supplier in your area, that has good business, and a site without any illustrations.
Try and arrange a meeting with the appropriate person and bring your portfolio. (Maybe even do a mock-up of a page from their site with your illustration to show a “before” and “after”?)
There is probably a demand for your illustrations, but I don’t think building a site and passively waiting for people to find you and decide to add illustrations in the way to go.