If you shop around you may be able to pick up a cheap 2nd hand petrol mower that will keep it in trim, but you'll need a strimmer or shears or even a scythe for a start off to get it short enough to mow - local Hire shop may be a good bet as you'll only want it once!
If you don't mind a bit of hard work an old hand mower (no engine apart from you !!) will be a lot cheaper to pick up & might not be so desirable to nick sorry I meant steal as no mower is desirable to me
