The cheapest waist-high fencing is Playground Fence, at $5/unit. You can completely surround a 60x60 lot with a double concentric path 2 units wide using 672 units of fencing, at a cost of $3,360, leaving a 52x52 area for use.
If you don't mind it looking a little funny, you can put the gates adjacent to the openings in the fence at night, so using them wouldn't save a burglar any time and you wouldn't pay $18 every time you delete/replace them (using the cheapest double-wide gate).
The reason I say this looks odd is that when you move the gates back to the center partition during the daytime, you'll leave a fencepost in the middle of an otherwise uninterrupted fence.
If you are starting out, you can still make a single, double-wide path around a 20x30 lot for about the same price as a burglar alarm, and this does work even better if your front door is opposite the fence gaps. Thanks, aws, for that tip.
At the point of guarding your legacy, though, I believe it's more about being creative and having fun than strict efficiency. Now I want to find out if the burglar gives up if he/she hasn't reached your door by morning...