Put down enough money so you don't pay PMI. It's like another $100 per month that buys absolutely nothing for you. It's an insurance policy for the lender in case you default.
Get the home inspection done early, and negotiate with the seller to fix the stuff they'll almost certainly find. Or have them knock $$ off the price, and you agree to fix things.
Since it's on a half acre, make sure you get a self propelled lawn mower. You don't need a riding lawn mower (if you don't want to shell out $2500+). Just get a push mower that has the self propelled option.
Good luck!