Great replies in this thread!
I will throw a wrench into things (pun intended) - depending on the age and type of vehicle, climate, or complexity of the repair, there are just some things that it's best for even the more experienced home-mechanic to not DIY.
I have attempted many DIY repairs on vehicles over the years, most were successful but not all. I'd say you can do 2/3 of most repairs without anything more than some jack stands, a jack, a good quality set of sockets, a good set of combination box/open end wrenches, a hammer, a breaker bar, some screwdrivers, and clamps. Helps to have a OBD2 scanner tool and a multimeter as well. WD40, penetrating oil, and brake cleaner are also borderline essential.
Nearly all of the failed repairs have been the result of either corrosion, tight spaces, or a lack of the right tool. Many times, it's a combination of all 3.
Most recently, I had a shop change out the front control arm bushings on my car. They were shot and failed state inspection. To remove them, I needed to take off a whole slew of suspension components - many of which were probably corroded on. I figured it would have taken me the better part of 6 hours to swap everything - and that's even if I could remove everything in the first place. For that job, having the car up on a lift makes accessing everything 100x easier.
A few years ago, same car, I needed to swap the rear bearings. The shop manual made it look like a breeze. It wasn't - all the bolts had stupid male Torx nuts on them, and they were all so corroded that even with penetrating oil and heat, none of them came off. I couldn't put it back together and drive to the shop, so I had to get a sawzall and cut all the bolts off and custom order new bolts to put back on. My car was out of commission for 5 days.
Longer ago, the thermostat in my dad's car went bad. Under normal circumstances, this is accessible and an easy job. On his car, there were two options to replace - remove the entire exhaust between the manifold and the catalytic convertor (or something similar), or loosen all the motor mounts, jack up the engine, and turn a 13 year old bolt 1/4 turn at a time, blind. He had the shop do it.
Even longer ago, we were swapping the serpentine belt on my then-car. We got it all off, only to find that the tensioner pulley was stuck and to swap it we would have needed tools we didn't have at the time - for that one, we charged the battery and drove to the closest shop.
Even longer, I had a car that had a busted rear shock. I was ready to replace it myself (my dad and I had done a few shocks/struts), but we had an uneasy feeling about it and not too much free time to work on it. Turns out the shock had been so badly damaged by whatever pothole it hit, that the guy at the shop we took it to said when the piston flew out of the shock and clean across his shop the moment it was unbolted. If we had been doing it in the driveway, there's a strong chance one of us would have ended up in the ER.
None of this is meant to scare anyone away from DIY repairs, just to illustrate that it's perfectly reasonable to pay someone else to repair your car even if the parts and tools required cost less than the shop quote - sometimes that price you pay for the expertise of the people working on it (and the tools they have at their disposal) far outweighs the savings on the job.