I'm trying to open my own ECU tunning small business, and I'm trying to find some open source or at least a cheap ECU flashing software(s) that works with:
-Modern Models of Chrysler, Dodge and Ford (Mostly: 300, Challenger, Charger and Mostang)
-Old models of BMW (Mostly 90s E30, E39, E32, and E34)
-Modern Models Of Nissan and Toyota (Mostly: Maxima, Altima, Patrol, Avalon and Camry)

I might buy HP Tuners for the US cars and PCM Flash for the Japanese ones. But if there are a cheaper alternatives that'd be awesome.

I guess I can figure out the .bin files remapping with winOLS, I'm just really having troubles with finding the flashing softwares.

If you could help me out and guide me to some softwares I'd be REALLY thankful!

There isnt one tool for alle.
Also E30, E32 and E34 arent flashable! They are everytime soldering oder socket job! So also extern programmer is needen for.
Tuning never is cheap!