I would think a riding lawn/garden tractor with at least 14 HP (16/18 preferrd ) and a 42" deck would be sufficient.
You didn't mention if your 1/2 acre is clear or includes your dwelling and other structures., either way, a 42 should handle it, you can go bigger ( more money ) and you need to consider WHERE it will take space, a mower ,gas cans
and such require more room than most people think. Leaving a mower out in the elements will shorten it's life span
very fast !!
As to brand of mower and which bells & whistles you think you want or need , you will find a large amount of folks on this site to offer their advice as I have... Whatever YOU decide ... best of luck, and keep us updated ...Boobala