First-timers tend to miscalculate the total tab for sealing the purchase and the cost of maintaining a home.

"Have a thorough conversation about down-payment costs and closing costs," Huss says. You need to know the total out-of-pocket costs.

Next, make sure you consider all the monthly charges. Online calculators on realty sites don't always include taxes, homeowners association dues, utilities, and home and mortgage insurance.

They certainly don't allow for flooring and window treatments, which your landlord covered previously.

If you're buying a fixer-upper, get several contractor bids so you know what lies ahead.

"You always have to be prepared, new or old, to make any repairs," Cecere says. If your mortgage is at 25 percent of income, repairs can bring your cost to 30 percent. 

"We always say you should have three months of basic living expenses in a very liquid place, and part of that is your house emergency fund," Cecere says. 

Finally, double-check utilities and tax costs to avoid nasty surprises.