Agree if the link is a nofollow then consider it, if its followed I would be to nervous about it.
If its nofollow find out how much traffic does the site generate, where does the site rank for the key terms.
If the site ranks number 1 (or top three) for 'window tinting' or what ever your targeted keywords are then go for it, however if you rank above them - whats the point potential customers would of all ready either seen your site and discounted it or been to your site and don't like you.
However that being said, if they rank below you but spend a lot on paid advertising, have a large email database and drive traffic that way it could be worth investing. The site might get a lot of direct traffic.
Forget SEO and put yourself in a potential customers head. Which site are you likely to see first the directory or your clients. Whats the customer journey.
Forget Google here - think of potential customers, they in the long run drive sales and Google second. I've never known Google by tinted windows before.