Second, how is your time? If you have time then DIY makes sense.
Third, I always buy the equipment used. I have several pieces that have more than paid for themselves because they were around to be used. Many little jobs go way faster because I have a backhoe around. Even made a crane attachment for it. A bit awkward but comes in real handy.
Fourth, you should be able to buy a used dozer for way less than $20,000 right now. I ONLY go Cat with tracked vehicles. You can still buy parts for ANY Cat tracked vehicle ever made. You may want a loader with a four in one bucket for your work rather than a straight blade.
I could not agree more. You are exactly right.