I have worked with my wife in the business and know others who have utilized their spouses or kids to help them with the biz. It's great if it works out because there are probably some tax benefits. I suppose it's to each their own. For me the key was 'part-time'. That is, I only worked with the missus for 1 or 2 days of the week. In the times when she worked more I would put her in with another crew. That's what worked for me anyway I think working with a close family member each and every day would be trying... especially if it's someone you also live with!
Consultant/Author, Start & Run a Landscape Business www.mowboy.com