There are a couple of good reasons why you should be friendly with home services companies. They know people - bottomline. They also have a strong handle on word of mouth referrals...
This seems to be the case for a lot of the ones I run into. I work with kitchen specialists, granite companies, and a lot of home improvement companies. It is usually the same scenario. A lot of these comapanies want to get the word out too about their services. They would like to do it with very little advertising costs.
Consider creating some space for these companies on your websites to drive traffic back to them. This has created some interseted exchanges between my clients and some home buyers that I know.
This works really well if your site is positioned well on the search engines.