Hi Pace, firstly before your friend goes and spends a load of dosh on the land, look at the place from the air, if it has lots of expensive houses directly around it expect complaints! As a land owner you can operate off your own landing site for 28 days per year, this is generally 1 departure and arrival, however if you are in a rural location you could do more, bit it will pay to keep a low profile, so don't invite the world to your new airstrip! A Robin 160-180hp will operate out of 450m safely with reduced fuel etc, although it will need to be housed, also a PA28-235 would do it or C182, however if you or your friend are not familiar with STOL then get some training!!. You can keep the plane in the corner of the barn, as long as the majority of the space is for agriculture and not a change of use(planning laws), if you need specific advice PM me.