Some relatively simple things I've repaired around our apartment. Not all of these people would replace, but they might call a professional when it's quicker and cheaper to DIY:

* Top-loading washing machine. If it spins really loudly, or stops spinning, pop off the front panel and check the belt. Ours had just slipped off. Just make sure you get it really tight when reattaching--I had to redo it a couple times until it stayed on. As a bonus, I found a bunch of clothes that had fallen inside, including my wife's favorite skirt :-)

* iPhone battery replacement. Just bought the iFixit toolkit and followed their guide, it was pretty simple. Extended the life of my 6s+ another year (so far).

* Clothes repairs are pretty simple. I've patched some pretty big holes in jeans with new fabric which is a bit more involved, but things like sewing buttons back on or patching small holes is really simple, just look up mending stitches online. If you don't have the right color of thread, you can use hidden stitches, or go for a kintsugi approach and make the mending visible which can be pretty stylish.

* Stove burner covers -- these literally pop out and are (usually) dishwasher safe.

* Dishwasher cleaning -- this isn't hard, but can be pretty gross if it hasn't been done in awhile. Look up a youtube video, take all the parts out and thoroughly scrub everywhere you can, then run a cycle with a couple dishwasher cleaning tabs. Night and day cleaning difference for old dishwashers.