I manage 22 units and do all the small jobs myself.
I have a general tool bag, a plumbing bag, and a bag for all my small circular saw, jig saw, multi-tool.
I use my general tool bag the most. In it, I have my impact driver with a 3.5 inch makita gold impact phillips on it(since i don't drill as much, I don't have my driver on me. I leave it in the garage). I also have a box full of different size screws, nails, washers, anchors. Then you have your general tools like a vice grip, hammer, channel locks, flashlight, tape measure, composite shims, headlamp, box cutter with extra blades, painter's tool 5-1, wire stripper, allen wrenches, voltage detector, outlet tester, lineman's pliers, good Milwaukee demo screwdrivers, Milwaukee 11-1 with Phillips, flat heads, and 3-4 common size nuts(this is great for appliances). I also have to have 4-8 pairs of vinyl gloves.
This ALL fits in my one Husky bag from Home Depot. I leave it in the back of my car behind the driver's seat. During the summer months, I also keep a tub of Advion roach gel for our multi-family rentals. I put out half a tub per unit.
If you're sure you're going to do it, buy good quality tools. Your debate is whether to go with the best of the best or go with mid grade tools like Husky or Kolbalt, which both have lifetime warranties. Milwaukee isn't really lifetime warranty(can't just bring it back to the store and get a new one), but I love their tools. I would not go with Harbor freight tools even though it has a lifetime warranty.
At home, I have a miter saw, shop vac, and a brad nailer from Ryobi. I love the brad nailer! It's cordless and it can shoot hundreds of nails before being recharged. I can do 1-2 rooms of baseboards easily without running out of juice. Baseboards make any room look great.
Get an account at Dunn Edwards/Sherwin Williams and buy quality paint at 25-30% off.
Good luck! I help clients who've just bought a house make their own tool bags or I gift them one as a closing gift.