If you build a great product, your customers will be your best advertisers.

That’s something Kevin Kiene has learned. The founder of ezLandlord Forms, an online provider of property-management legal documents, remembers a time before that lesson was entirely his.

“In the beginning, we were marketing and advertising before we had a great product,” he said of his Web site, which will turn three this August. “We have a great product now.”

There were usability and design concerns and nowhere near the breadth of options the site now offers. But a lot can change in three years.

Last month, they launched a complete site redesign and are in the process of becoming a green certified business and doubling their staff. This month, they surpassed 300,000 members, many of whom are paying into its subscription model, pushing year-to-date sales by more than 225 percent. In September, HGTV’s Designing Spaces will be shooting a segment on the site to air at the year’s end.

“Business,” Kiene says, “is good.”

The company, which has office space in Cinnaminson, N.J., currently features seven employees who work from their homes across the country, including a Willow Grove-based Web developer and Kiene, 40, a native of Fox Chase in Northeast Philadelphia.

But Kiene, who now lives in Frankford, is proud to talk about the site’s national appeal, in addition to its growing traffic and how the idea for ezLandlord Forms came to him because he could never find a lease that would square away who was taking care of the damn lawn.

“It came out of a need, being a landlord for more than 15 years, knowing that I couldn’t always find a good lease agreement that could really protect me,” he said. “You’d call a friend who is a landlord, or you contact a real estate agent and say, ‘Hey do you have a lease? I need a lease.”

What lease documents he has bought were rarely up to date, Kiene says, and they rarely detailed responsibilities like cutting the grass, shoveling snow and switching batteries in smoke alarms. So he created his own basic lease and added or subtracted items and details as he saw fit.

That formed the core of what has become what Kiene says is the largest, most comprehensive property-management legal document resource on the planet.

It’s a subscription model: two weeks for $25 designed for one property; six months for $40 and one year for $76. It costs less than $10 per year to add an additional property. Membership gives users access to, as Kiene puts it, “the whole ball of wax.”

That includes the site’s robust Lease Builder Wizard, which puts users through a checklist of details to create a state-specific, tailor-made lease agreement, and its state assist features, guiding users through different laws, practices and expectations from state to state, including how large a security deposit, return-check fee and pet fees.

The site also has a network of real estate attorneys from each state, and just about every property-management document with a wide variety of details. Of course, the site’s staple products are its rental agreements.

“If you have to buy each form, is it really worth it?” Kiene says. “We give you a central source.”

Below, watch an animated tour of the company’s development, which cost a cool $20k, Kiene says

Kiene says he’s proud to be building this business in his native Philadelphia. (He says the above video was made by a Chicago-based firm, which plunked in the New York and Windy City references, much to our displeasure.)

It’s here where he found his real estate experience. At peak, he owned 10 rental properties in other parts of Northeast Philadelphia and “Kensington in the beginning,” he says. Now he says he’s filling a new role in a trade that became his career.

And Kiene isn’t done growing the site. He wants to develop a premier and secure resource for tenant credit checks and eviction history

“We want to build the best system,” he says.

That’s how your users will spread the word about the good work you do, he now says he knows. He continues to have the site’s usability tested, with the help of volunteers, and he keeps plunking down money that he says could score him the big suburban home some might dream of over a modest Frankford rowhome.

“Four years ago, this was just an idea. It took a year just to get the product together,” he says. “We have more to do, but there’s still nothing that comes close to what we offer. There’s nothing more important than that to me.”

Every Monday, Technically Not Tech will feature people, projects, and businesses that are involved with Philly�s tech scene, but aren�t necessarily technology focused. See others here.

And the audio-book Web retailer, which saw its revenue triple from 2004 to 2007 and ships mostly self-improvement merchandise, is doing it from 12th and Callowhill.

For that, Stroll is getting some congratulation. Along with three other Philadelphia companies, it was named to the 11th annual Inner City 100, a competitive ranking of the fastest-growing companies located in the “inner city” of a U.S. metropolis, last week. See what constitutes an inner-city here.

Only Denver and Boston, each of which had five companies headquartered there, were better represented. See the complete list here [PDF].

The list comes from the Initiative for a Competitive Inner City, a national nonprofit organization founded in 1994 by a Harvard Business School professor. The organization’s mission is to promote economic prosperity in U.S. inner cities through private sector engagement leading to job, income and wealth creation for local residents.

Stroll, ranked 62nd, was accompanied by the following four companies: its Callowhill community neighbor Avencia, the geographic analysis and software development firm that was ranked 13th; East Frankford design collaborator and fabrication company Amuneal, ranked 51, and Perryman Building and Construction Services, which was ranked 94th and is based in West Philadelphia at 45th and Market (help me with what neighborhood that is in the comments below).

The Inner City 100 list has no industry specifications, but from Stroll’s Web base to Avencia’s software development and the high-end design and fabrication of Amuneal and growing sustainable requirements of construction for Perryman, all four of Philadelphia’s representatives could be considered members of our region’s creative economies.

Stroll’s neighbor Avencia, no stranger to Technically Philly, was the highest ranked Philadelphia firm, at 13th. Their five-year compound annual growth from 2003 to 2007 was 647 percent. No decimal point needed.

Philadelphia was better represented than each of the five cities with larger populations, see at right. No New Jersey or Delaware companies were listed.

Other cities represented by multiple businesses include Detroit, Miami, San Diego, Baltimore and Buffalo.

Pennsylvania was the third most decorated state with six company nominations; Philadelphia was helped out by two from Pittsburgh. California was by far the best represented state, with 15 companies, followed by Massachusetts with eight.

Collectively, the 2009 Inner City 100 grew at a compound annual growth rate of 40 percent and an average rate of 324 percent between 2003 and 2007. More than 5,000 nominations for the 2009 list were received. The top 100 have employed nearly 17,000 people and created nearly 10,000 new jobs over the past five years.

See additional facts about the annual list here.