Looking for sound advice

[EddyCurrent]

You don't need to fear using aluminium and steel. I bought a sheet of 20mm thick aluminium, some 100x50x6 aluminium box section, 50x50x3 steel box section, 50x100x3 box section, 30x6mm steel bar, 50x10mm steel bar and various small pi6ces of 3 to 6mm aluminium plate.
The steel was cut with a small angle grinder and these disks Toolstation > Power Tool Accessories > Cutting Discs > Multi Purpose Disc
The aluminium was rough cut with a saw like this Amazon.com: Hitachi CR13V2 10-Amp Reciprocating Saw: Home Improvement then it was cut to size on a woodworking bandsaw with a metal cutting blade.
Welding can be done with a small machine and all other tasks with a drill press.

So in reality you do not require a huge array of expensive tools to get the job done in house.