When first-time buyers start looking for a residence, it's easy for them to get fixated on how much the monthly mortgage payment will be. However, it's important that the supplemental costs of owning a home do not get overlooked.

According to a recent analysis by the real estate site Zillow and the professional services resource Thumbtack, the average homeowner pays $9,394 a year in additional costs. This figure is based on a median home value of $217,300 and accounts for property taxes, homeowners insurance, utility bills, and maintenance costs.

"Ongoing maintenance costs and annual fees are some of the most common surprises for first-time homebuyers after they finally become homeowners," said Aaron Terrazas, senior economist at Zillow. "While they are shopping, buyers tend to focus on their monthly mortgage payments, but other needs quickly add up after move-in. The list price is just the beginning of understanding the costs that come with being a homeowner, and it's important to understand what other expenses you may have to account for when determining what you can afford."

Zillow's Consumer Housing Trends Report for 2017 found that one-third of buyers considered budgeting for homeownership to be a challenge. This was particularly prevalent among millennials, who are entering the housing market in increasing numbers, with 43 percent saying it was difficult to determine how much they could afford to spend on a home.

The analysis said the typical homeowner spends $6,327 a year on unavoidable costs. These included $3,001 on utility bills, $2,239 on property taxes, and $1,087 on homeowners insurance.

These costs varied considerably across different markets. In San Jose, Calif., the most expensive market in the United States, the typical homeowner needed to budget an additional $17,255 per year for necessary costs and $3,400 for maintenance on a median priced home of $1.29 million. Indianapolis had the least expensive supplemental costs of the 35 metro areas included in the report, with an average of $5,540 required each year for necessary expenses and $2,680 for maintenance on a median priced home of $152,800.

Chicago had the highest property tax rate of the metro areas, with a median priced home of $220,400 requiring $4,588 in property taxes per year. New York City had the highest property tax expense overall at $8,164 for a median priced home of $429,300. Property taxes were lowest in Phoenix, Ariz., requiring an annual payment of $1,474 on a median priced home of $254,700.

The more expensive markets also tended to have higher homeowners insurance costs. San Jose homes typically required an annual expense of $6,438 for insurance, while San Francisco homeowners paid $4,768 for insurance on a median priced home of $953,600.

Utility bills were less variable. Minneapolis homeowners had the lowest annual expense on average, paying $2,265. Atlanta homeowners paid the highest average cost for utilities at $4,612 a year.

The report also estimates a more avoidable annual cost of $3,067 on maintenance expenses. These included an average of $1,704 for house cleaning services, $780 for lawn care, $225 for pressure washing, $130 for gutter cleaning and maintenance, $108 for HVAC repair and maintenance, and $120 for carpet cleaning.

"Many basic maintenance costs are often overlooked when calculating the cost of buying a home," said Lucas Puente, lead economist at Thumbtack. "It's imperative that those looking to buy a home do their homework to avoid any surprising charges."

Maintenance costs also exhibited less change among the different metro areas, although differing labor costs caused some variation. The combined services had an average cost of $3,070 a year in Portland, Ore., the most expensive metro area for maintenance. Miami and New York City tied for the lowest maintenance costs with an average of $2,570 a year.