Just buy a basic washer and dryer, no bells and whistles, available anywhere they sell appliances, brand not that important, it will last a very long time, maybe will need to replace a belt or a knob every 5 to 7 years or so, depending on how you use it.
I use to have several rental properties, I learned this the hard way, no frills no ills.
I will recommend getting a gas dryer if possible. They are even simpler than the electric dryers due to the absence of the electric heating coil.
If you can find a washer with the simple electro-mechanical timer control system instead of a computer board I would buy one. They are not susceptible to the power surges that others on the thread have mentioned.