I bought an old (1970s) backhoe for my property on advice from this forum and I love it but (and I think it’s a big but) I get a kick out of working on these things. I also am very bad at planning in advance to know how long to rent an excavator, and know myself- if I rent it for a day I will work too late on that day and risk the machine or myself when I get too tired and haven’t finished the task I rented it for. Owning mine is much more relaxing for me, even if it’s been sitting with a seized transmission for the last 6 months.
If you’re thinking of buying an old big machine, I’d recommend watching some Farmcraft 101 on YouTube, and maybe a little bit of Diesel Creek on YouTube to see if working on it sounds like fun rather than like an obligation, because obligation is poison.
If you don’t think you’d get a kick out of working on it, I’m gonna strongly agree with everyone else- do not buy one of these new, do not buy a cheap mini backhoe from alibaba for $4995, do not buy an old one and hope/pray/expect that nothing will go wrong. Lease what you feel comfortable operating, hire out what you don’t.