Whatever you do, make sure you have REPLACEMENT insurance.
My neighbors, or someone my neighbors knew, stole my John Deer 420 (early 80's model lawn and gardon tractor - all it ever did was mow grass but it did have a PTO and such) ~6 weeks ago. It was kept outdoors chained to a moderately sized oak tree ~15 feet from the property line with a thick chain and a decent padlock. It had a replaced low-hour engine, but was still worth only ~$2500.
My experience:
Storing the "tractor" outside for 5 years, largely unused, did more damage than the previous 20 years in the garage with regular use. For my new tractor I'm starting with one of the fabric "tent" garages and putting a permanent structure on my priority list right behind a good fence.
If it's stolen, you won't get it back. Despite the drag marks going from my yard into my neighbor's yard and their statement to the sheriff that they had seen somone in a red pickup in my yard at ~3:00 in the morning where my tractor used to be, law enforcement did nothing more than file a report and tell us too bad and not to expect to ever see it again. Considering the neighbor's statement and the drag marks, that means that they had someone in a red pickup in their yard as well at 3:00 in the morning ... and if they didn't know whoever drove the pickup they would have most certainly shot them on the spot. I'd have liked them to at least look around their yard for some sort of evidence, but they didn't do anything other than take their statement (thank goodness they are moving soon!).
Because we had replacement insurance, our homeowners policy covered us for what, in their judgement, an equivalent tractor would cost new today. Take that number minus our deductable, and we have ~2/3 of the money we need to pay for a new Kubota 3400HST with all the attachments we'll need for the next 3-5 years.
On top of our homeowner's insurance, we are financing 100% with Kubota (while our $$ draws interest in the bank) and using their insurance program, which will cost us ~ $100/yr give or take.
My summary: Out of sun, out of sight, get good insurance, and either pray for good neighbors or be thankful for the ones you already have.