Well, you won't get it done like that.
Start with buying some of the equipment you would need, like a welder, drill press, angle grinder, maybe a plasma cutter or oxy-actelyene setup. And start learning how to do it, read up on how to weld or take an evening course, make smaller stuff that is useful, but not necessarily as strength/design critical as a backhoe.
And it doesn't have to be perfect right away, either. You make it, use it for a bit, and something fails or doesn't work as well as you'd like, you'll have the tools to fix/modify it to work better for you.
Three years ago, I didn't know how to weld, but bought a mid-size MIG welder (Miller 211), and since then I've made things like ramps to load equipment in my truck, fixing the tongue on my trailer, fabricating the mounts for the front axle for my truck (I upgraded it to 4wd), smaller mounts/holders/enhancements for equipment that was designed cheap instead of good, a custom grinder to make it easier to sharpen mower blades, a mount for a snowplow for my walkbehind mower, and now I'm working an building a power vacuum.
The ramps I had to make twice, first ones were too flexible, mount for the diff took some time and thinking, as I'm still not very skilled at welding upside down, so it was a lot of measuring/test fitting/back to the workbench to weld/grind/repeat, it's up to 4 or 5 revisions of the plow mount now.
Most of the things I could buy, but for a lot more money, and it wouldn't work as well for me, compared with what I made.
So get cracking!
You just need to start with something, and then it kind of drags you along for the ride...