If you went with a common US brand you can get a good system with 4 units and a 36,000 BTU heat pump unit for around $6,500 USD installed.
I don't love the wall units - they're pretty ugly, even the new ones. If you're getting a mini-split, the in-ceiling or wall cassettes that are hidden are really the way to go IMO.
I got hung up on the excess line set idea and did a full DIY install of a non-DIY model mini-split. I bought, borrowed, and rented a lot of tools, spent a lot of time researching and learning. I really wish I went with the DIY model.
Despite that lesson, I may do it again when I finish my attic space, but this time I'll add copper line brazing to the list.
I’m mostly curious how these DIY units compare to Mitsubishi, which seems to be what all the installers recommend.
There are also DIY variants where a fixed line length comes from the factory with either a vacuum or a refrigerant in the line. The lines have metal seals on the fittings that are ruptured when torqued down on the equipment.
Stuff I had already specific to HVAC:
-R-410a manifold, gauges, and hoses.
Stuff I went out and bought:
-Nitrogen tank pressure regulator and hose for HVAC.
-Mandrel pipe bender
-Flaring tool
-Micron vacuum gauge
-A slightly better copper pipe cutter and deburring tool.
Stuff I rented/borrowed:
-Vacuum pump from Autozone. Free. It was plenty big enough for a minisplit.
-Full nitrogen cylinder rental from Airgas.
Things I'm glad I did:
-Used a wall mount instead of a pad for the compressor unit. Unit stays clean.
- Pressure testing with nitrogen. It's worth the money and effort to know up front it doesn't leak.
-Followed a more thorough procedure for vacuuming/drying which involves vacuuming down several times and flushing with nitrogen. I got a much better vacuum after subsequent flushes.