Grunching, but my own lessons learned:
1) Homeowner associations have their benefits, but as time has gone on they're more a PITA. They can be very inefficient and boards elected from random residents can be especially bad.
2) Replace your water heater at the first sign of trouble.
3) Fix any leak anywhere immediately.
4) You need to have your ducts and cleaned every now and again, maybe 10 years, but find a reputable NADCA-blessed place. Price varies by house but for some amount ($400) they'll clean out your furnace and clean your returns. It's not supposed to be a big deal health-wise in most cases but it does help with dust.
However, beware all of the fly-by-night duct cleaners advertising $89 specials. Most are ****ty if not scams, and do the bait-and-switch with prices. Plenty of details online.
5) Same with dryer vent.
6) If you're not particularly handy at all, or tend to cut corners, then leave these for pros: plumbing, HVAC, major electrical, installation of cabinets and counters, flooring, or subflooring. Some exceptions: installing a basic toilet, putting down groutable stick-tile (TrafficMaster Ceramica) on an already-level floor, or changing light fixtures/outlets/switches which is easy.
7) Good tools to have:
- Cordless reversible drill with a variety of bits
- Actual screwdrivers
- Set of Allen keys
- A good wrench
- Lineman's pliers
- Needlenose pliers
- Outlet tester
- Hammer
- Prybar
- Wire cutter/stripper
- Duct tape
- Electrical tape
- WD-40
- Little tin of lighter fluid/naptha
- Fine grade steel wool
- Some drywall screws
- At least a little DAP Drywall patch kit
- Simple drywall saw
- $35 4.5" angle grinder + a $30 blade
- Tape measure
- Paint-mixing drill attachment
- A level, or better yet two in different sizes
- Stud finder and no your wife/gf doesn't count
- 2 ft & 6ft A-frame ladders, possibly a larger one depending on situation
- Sanding block, some 200 grit sandpaper
- Simple wood shims
- Fire extinguisher
- Crazy glue
- This particular utility knife
I'm sure I left a few things out but that's most of it, covers the basics that come to mind.
8) Walls are almost never perfectly even. For example, the corners in a given kitchen are often not perfectly 90 degrees and flat which can make cabinet installs tricky.
9) If you ever install a shower or wet area, use what the pros advise for a wet area. Some DIYers will use easy pre-mixed tubs of stuff (mastic) to set shower tiles in rather than getting a bucket and mixing up some proper thinset. The problem is mastic tends to be water-soluble.
10) Lowes and Home Depot are really cool about returns, even after a while and without a receipt. 10% off coupons are always available on eBay.
11) If you live in a cheaply built condo or townhouse, avoid putting any especially heavy furniture near the center of the room. A heavy wood chest with 100 pounds of stuff in it at the foot of the bed might sink the floor a little bit. The joists might be further apart and plywood can bend.