There's a reason you fall in love with a new-construction model home the moment you walk inside: Someone is paid to design the house in a way that evokes such emotion.

Interior design is a booming business in real estate and the residential building industry. The goal is simple: to seduce a potential buyer into believing they cannot live without the house -- no matter what the cost.

Builders allot large budgets that enable designers to shop for furniture, art and other touches that make a model home look perfect, but not so perfect that a potential buyer would think it can't be replicated.

Designers also use tricks to make a house appear larger and more desirable. An obvious one is using mirrors, but some designers have small furniture custom-made -- a pricey endeavor -- so that it doesn't overpower a small room.

Another trick is putting bright flashes of color in the middle of a room. Your eye is drawn to the object or objects, and therefore, the walls appear to be pushed back.

Still, most of the money is spent on decorations such as window treatments, rugs, pillows, plants and lamps.

Pamela O'Neil, a model home designer for numerous residential builders in the Detroit area, does most of her shopping online and often tries to recycle things from house to house.

"It isn't always what you spend, it's how you put it together," O'Neil said. "I can go to Gorman's [furniture store] . . . or Kmart; it makes no difference to me."

O'Neil said it typically takes her up to two months to design a home from start to finish, but she has also done it in 21/2 weeks. She is careful to consider where the model is and the asking price before she determines a decorating budget.

For a house or condominium that costs about $150,000, O'Neil said she could spend $15,000 to $20,000 on design. For a $350,000 home, a $75,000 decorating allowance is the bare minimum.

"I'm very much into detail," said O'Neil, who owns Innovations, an interior decorating and display company. "You have to splurge on certain things. A model home appears cheap if you don't do anything to it."

Robert Mitchell, a sales agent for Seville Homes Inc., one of O'Neil's clients, said often a buyer's first impression is worth the cost of the decorating. Sometimes buyers ask if the model can be sold as is.

"It has made a huge impact on our sales," Mitchell said. "For a potential buyer, it allows them to see what a house can become."

O'Neil added, "Designing a home helps sell it -- it becomes an emotion."

Still, O'Neil said she does cut corners. She uses inexpensive wallpaper and frames it with crown molding. Also, she uses wallpaper to create the illusion of a headboard, instead of buying one.

Here are some of her tips for making your house look like a model home:

* Stay away from trendy, overstuffed furniture unless the room is large enough.

* Don't be afraid to use color.

* Make a fireplace a focal point.

* Try to shake up your home's design every two years. Even if you can't replace big items such as couches, inexpensive decorations such as pillows and rugs can be changed.

* Don't get locked into trends; they change too quickly.

* Don't ignore a kitchen; it's the heart of the home.

* Get ideas from magazines that can be replicated easily and inexpensively.