First, let’s point out that a large minority of single engine planes are owned in partnership of two to four pilots. So, for the ensuing discussion, please divide the costs accordingly.
To buy a plane intelligently requires some research. First, what do you want to buy? Most new pilots buy an entry level plane as a means to build experience in a low workload environment. Heck, even a slow plane is often 3 to 4 times faster than the fastest car in the real world, so that looks pretty good. I would suggest the following steps to make your decision. First, select the make and model you want. As you get into aviation, you can rent, borrow, and cage rides in a variety of aircraft to get an impression of how you like them. Second, buy a book called The Illustrated Guide to Used Airplanes and read about potential buys. This book discusses how the planes are aging and what to look for when buying, as well as any quirks in flying them. Third, subscribe to Trade a Plane and research the market. Last, get a good pre-buy inspection. Windsong will walk you through your first buy at a greatly reduced rate for former students, particularly in helping you decide what to buy, locating a good prospect at the right price, and in getting the pre-buy inspection, as well as pick-up and delivery. The Windsong personnel have several lifetimes of experience in this realm.
To own a plane requires that you keep it in good repair, which is usually not a large budget item on a yearly basis. However, you must also have an annual inspection, which costs anywhere from $500 up. The plane must be signed off by an federally licensed inspector before it will be airworthy for another year, and that means no discrepancies of any safety related item. An average annual inspection on a fixed gear single runs about $1200, after parts (tires, spark plugs, filters, etc.) and labor and discrepancies.
Of course, you will also want insurance. An instrument rated pilot will pay about $600-$800 per year on a typical entry level plane. This will be a million dollar liability policy and full coverage on the aircraft itself.
Tie down outside at most county airports is $15-$40 per month.
So, all in all, sunk costs are about $2500 per year.
Fuel costs go up and down, mostly up. The variance between one airport and another can be large. For instance, avgas sells at one local airport here in Tennessee for $4.91 (about $1.35 more than car fuel) as I write this. However, a pilot who buys from the big FBO in Nashville will pay more than $7.00. Planes use about double the fuel per hour, compared to cars. Of course, even a slow plane averages 2.5 times the speed of a car over the distance, so you get there a lot sooner and turn the plane off. It doesn’t actually even out, but it’s close.