Backhoe: I used a mini-excavator (8000 pound) to dig 400' of 4' deep waterline trench on our property, which grows granite boulders like a potato farm. I only ran into one boulder that I had to go around, but I was able to dig out many many many boulders the size of kitchen ranges with that mini-ex. It just took a little bit of time working at it. It ripped through clear soil. Way more maneuverable than a backhoe. To figure out how deep you need to go, just search for trustworthy frost depth or frost line maps. Sometimes, you can get a free days rental on equipment (Sunday) if you rent it over the weekend. Basically, you pay for Friday and Saturday, but they are closed Sunday so they can't charge you. Better yet, make friends with someone who owns an excavator. Just make sure to figure out how long you think you will need the equipment. Then, double or triple your estimate, because the weather will be terrible and it will take the rental company all day to send their guy out there to replace the hydraulic hose you break first thing in the morning, plus he brought the wrong one, so he'll be back out by 4 or 5.
Security: Having a cabin that looks run down might actually make it more of a target to thieves, or even worse, neighborhood teenagers. Lots of people put cellular game cameras up all over their remote property to deter and catch criminals. Cheapskates duct tape a spare baofeng handheld ham antenna to the back of their old memory card game camera with no batteries and mount it in an extremely obvious place.