If wishing can make it so, home buyers will pay a median price of $65,446 this year for a new house, situated on a sizable lot of half an acre or larger. Monthly housing costs -- for mortgage, utilities, taxes and insurance -- will average $514.

These revelations are among the results of the latest annual survey conducted nationwide for Professional Builder magazine to attempt to learn what active home buyers (those seriously considering buying) expect in 1981.

At the time of survey, mortgage interest rates averaged 11.6 percent nationwide, and more than half of the home seekers found that rate acceptable. Today's interest rates average 16 percent, and consequently an estimated 85 percent of America's families have been shut out of the home market, according to housing experts.

But it's still interesting to note what plans home buyers and builders were making when interest rates were at an "acceptable level." Among the survey's findings:

Style. Ninety percent of the buyers want a single-family detached home; 49 percent of them want a one-story home, 25 percent a two-story, 20 percent a split level.

Price. Buyers said they expected to pay a median price of $65,446 for a detached home, but a median price of $75,000 for an attached unit. The builders agreed with the buyers' expectations of higher prices for quality attached housing. The median prices of the builders' best line for 1981 is $75,700 for a detached house and $80,832 for an attached.

Down payment. Nearly one-quarter of the buyers said they could afford a down payment of $40,000 or more. The national median down payment is $20,000 for 1981 compared with $18,137 in 1980. First-time buyers said they could put down an average of $9,240 on a new home; present owners $30,990, with most of that money coming from equity in their current homes.

Mortgages. Nearly 82 percent of the buyers want a conventional fixed-payment mortgage, but 18 percent say they prefer variable rate or graduated-payment mortgages.

Payments. The monthly cost of home ownership is the most important factor in the buying decision of most families seeking a home. Most buyers said they could afford more than $400 a month, but only 16 percent said they could afford more than $750.