My advice would be to find a good used mid size track loader and enjoy it for your personal use.
But don't expect to make it a profitable side income. It takes years of experience to become proficient enough to hire out, plus you will need other equipment for that. Like a dump truck and HD equipment trailer, just for starters.
But a track loader can do so much more than a dozer and once you get the hang of it you can ditch, bank and terrace as good as any dozer with a 6 way blade.
