After 15 years of business partnership with his wife, Roger Bates has some simple advice for how he makes it work.

"All you need is this: 'Yes, dear,'" he joked. "Once you learn that, everything is wonderful."

"He doesn't quite live up to that one," said his wife, Traci Bates.

"Yes, dear," Roger said.

Whatever their strategy for getting along, it seems to be working. The couple said this year will be their best yet in sales for their Vista company, LifeCORE Fitness, which manufactures and sells fitness equipment, including ellipticals, rowing machines and exercise bikes.

They expect to do about $9 million in sales, up from $6 million in 2008 and 2009. More than 250 stores across the country sell LifeCORE machines, which they distribute from a 18,000-square-foot warehouse, Roger said.

That warehouse is a big jump from the place where Roger originally used to sell fitness equipment ---- his garage. He began selling equipment 17 years ago in Los Angeles, which is where he met Traci, who was then his neighbor.

Traci was doing bookkeeping for a restaurant at the time. The two started dating and soon decided to go into business together. They said the decision to pursue a fitness-based business was natural, both because Roger had experience selling exercise equipment and because fitness was a common interest.

"When we met and started dating, we were always very active," Traci said. "And selling people fitness equipment is something you can feel good about doing."

The couple moved to Dallas and opened a fitness store, with Roger in charge of sales and Traci managing accounting.

"We became a thorn in the side of much larger competitors," Roger said.

The couple sold that business and returned to California to open a fitness retail store in San Marcos. Their experience selling exercise equipment helped them develop their LifeCORE products, which they began selling six years ago, Roger said.

"People really want something that is compact, that can actually fit in their house," he said. "We have that."

Roger also said the equipment hits "key price points," because it has better quality than the cheapest exercise equipment, but with prices between $800 and $3,500, still costs less than most high-end machines.

"To succeed, you have to have a better mousetrap," he said. "You can not sell the same product as everyone else, or you will lose."

The couple said they had so much success selling their equipment to retailers across the country that when the lease ran out on their San Marcos store, they decided not to renew it.

"Our business had grown to a point where we couldn't do both," Roger said.

The pair plan to expand their sales to more specialty retailers, along with larger stores like Costco and Sears.

"We don't have a lot of fear that we will fail, because we have an overwhelming belief in what we do," Traci said. "In every step of our journey, it didn't occur to us that it wouldn't work out."

Their success so far has helped make their business partnership and marriage run smoothly, Traci said.

That, and one other thing.

"Our offices are on opposite sides of the building," she said.