Even when you're making a lateral move to a similar-size house, moving can cost a fortune -- professional movers, a truck, someone to guard your stuff if you live in New York City, maybe some time off work. Getting your car to the new place if you're moving cross-country.
If you need to buy a smaller couch, smaller dining room table, smaller bed, smaller rugs and replace a triple dresser with a double, moving's going to cost you a whole lot more.
Having to buy all new furniture (and hire a decorator, if that's your thing) will tack on significant expenses to your downsize, so make sure you'll still be saving money after redecorating. Otherwise, if your reasons for sizing down are financial, you might need to come up with a new plan.
To determine the cost-effectiveness of your move, you'll have to take a hard look at your monthly expenses…