By JOYCE M. ROSENBERGNEW YORK (AP) â¿¿ As Lauren Smith and Matt Hendrickson drive home together, all conversation about work must stop a few blocks from their house. The couple came up with the idea after starting a business together. "That's our cutoff point, so when we go into the house, we can have a normal personal life," Lauren says. Marriage and other long-term relationships aren't easy. And running a small business is no picnic. Putting the two things together can make life complicated for the happiest of life partners. Still, millions of people run businesses with their significant other every day. It's not known how many couples own and run a business together, but the number runs into the millions. The most recent Census count, in 2007, showed 1.4 million companies that were co-owned and equally operated by husbands and wives. That doesn't include businesses owned by unmarried domestic partners or same-sex couples. The Census counted another 2.3 million companies owned by spouses but primarily operated by either the husband or the wife. There's no formula for making a success out of a business that is owned by a couple â¿¿ or for also keeping their home life happy. Many couples make disagreements part of their decision-making process. Some set their egos aside and listen to one another. And some, like Smith and Hendrickson, find that they need to take a break to keep working well together. _____ SETTING LIMITS Smith and Hendrickson started Ascendify, a San Francisco firm that helps companies add social media to their online job postings, in April 2012, less than a year after they were married. Matt brought 20 years of high-tech experience. Lauren had worked in advertising. Building a business together has its perks. Long hours working on a startup leaves little time for much else, the couple says.