Susan Gregg Koger began collecting and selling vintage clothing online the summer before her freshman year of college in 2002. Since then, she and her then-boyfriend (now-husband), Eric Koger, have transformed the business into a fast-growing online clothing retailer, ModCloth, with more than $100 million in annual sales and some 400 employees in three cities. Over the years, the pair have made every significant decision together. That doesn't mean everything has gone swimmingly, though, as they explained to Inc. senior writer Christine Lagorio-Chafkin.

Susan: One thing that's really served us well is that whenever we are making really big decisions, we always sit down and talk through what the worst-case scenario would be. But for some reason, we didn't do that when it came to our office space.

Eric: In 2010, we decided to move out to Los Angeles to be closer to our designers. And we heard so many good things about San Francisco that we decided to become a three-city business that year. We didn't know what we were getting ourselves into. Just having two cities is way more than twice as complex as one.

Susan: And three is exponentially more complex. Turns out, it's really expensive to relocate about 30 people. We also failed to test-drive the spaces before we bought them. Making sure the air conditioning works, things like that. Our Los Angeles office was always so hot or so cold. Our Pittsburgh office wasn't soundproofed. It was really hard to have a private conversation. You need to try before you buy.

Eric: The irony is, we do this pervasively in our business. We put samples in front of customers before we invest heavily. And we beta-test and progressively roll out all new technologies. But when it came to offices, we were like, "Nice space! Signed!"

Previously in Inc.: Eric and Susan Gregg Koger were on the "30 Under 30" list in 2009.