Affordable worry free car?

I'm looking for something in the 2012 range. I've narrowed my budget to about 12,000. Honda Accord, nissan altima and chevy malibu. Something that looks decent, good gas mileage and a vehicle that won't end up in the repair shop than on the road would be ideal. I'm 23 married no kids also in the military if that makes any difference
Open to all other car make & models

I recently drove a 2015 Malibu rental, My 2011 Honda Accord was in the shop. Man I couldn't wait to get my car back, even though a big car the Malibu felt cramped to me. Ride is a lot better in my Accord, passing on uneven road was sketchy in the Malibu, would torque steer like mad. For my personal choice Honda Accord is best, as Honda legendary reliability too.

There isn't a worry free car. Especially a used one

Its difficult to know in advance if a car is going to be worry free in advance as cars wear as they age.

The accord and Altima are generally a good cars and so is Mazda 6. I would take a LONG test drive and if you still like it, have a mechanic check it before you buy it.

I would put Malibu below the others but it might be cheaper?

Do you need an expensive car if you are going to be on ships?

There are no worry free cars. Any car has the potential for problems. A Honda will be less likely to give you problems than the other cars you mentioned.

Forget any of those on the list and look at toyotas instead… A MUCH better choice

You really can't go wrong with a well cared for one owner Honda Accord. Don't forget Subaru and Hyundai.

But you have to understand that All CARS, regardless of make or model is going to require scheduled routine maintenance in order to keep the car running good. You can't ignore the manufacturers recommended maintenance schedule.

The cars you listed should meet that criteria as well as any, however there are no "worry free" cars. That is why manufacturers offer warranties.