Walleye asked for as primer on prepping onions for storage. This is pretty simple to do.
First grow the right kind of onion. Yellow and red onions are great candidates for storage. Sweet onions, not so much.
What we do is cure them before we store them. This involves pulling the onions when the greens have fallen over. You can wait up to a week after the greens have fallen before harvesting. We put the onions on a drying rack of some kind until the greens have turned brown and dried up. Once this has occurred we clean up the onions by removing the top layer(s) of skins that are dirty (but we are careful not to remove too many layers because the onion needs the skin for protection while in storage) and removing the roots by hand pulling them. Be careful with the onions as they do bruise fairly easily and once bruised will not store for more than a few months before rotting
A drying rack is anything that will allow air to circulate all the way around the onions. Eugene made a nice rack last year out of old fridge racks and wood, it has 6 shelves about 1.5' apart and stands about 7' tall. Before that we used hammocks made from chicken wire and other small fencing. This year we will probably have to make a few hammocks out of plastic snow fencing because I have already filled up the drying rack with just 2.5 beds of onions out of 15 beds (we have a great crop this year and planted a lot more this year than in the past). It is essential the onions be in a dry airy place out of direct sunlight that is protected from rain. Onions cannot get wet while curing. A garage or barn is great. In your house would work but know this is a dirty process and you will end up with lots of dirt, onion skins, dead greens and dust all over the place. If you are a married man thinking the house will work for curing remember this sort of thing will piss off your wife. Trust me on this, I have a very, very high tolerance for dirt in the house (we used to bring chickens in on occasion, store all sorts of produce and even clean onions and garlic in the house) and I would never let Eugene cure onions or garlic in the house. Indoor curing could cause divorce so keep this out in the garage, barn or shed.
Once the onions are cured we store them in bushel baskets, these neato waxed produce boxes, that were given to us last year by a friend who trucks items including produce, or plastic produce crates. I would not use 5 gallon buckets as they do not breathe well enough for onions.
Onions are still alive so need a cool/cold place that is dry. They like it between 32F and 50F with humidity around 50% to 70%. If it is too warm (above 50F) they will sprout early and than rot. They can freeze as long as they are not disturbed while frozen and be just fine. If you move them while frozen they will bruise and the bruises will rot and ruin everything.
Sweet onions such as Ailsa Craig, Walla Walla, Vidailia, Granex, Superstar, etc., are not suitable for storage. These onions will a best store 3 to 4 months in he fridge or 2 months at room temperature so we do not bother curing them. We just pull them and cut off the greens, remove the outer skins and the roots and use. We store these onions in the fridge unless they will be sold/used within a week or three.
Another note on cooking onions. For some reason the sweet onion PR folks have been telling the public that sweet onions are great for cooking. They have even duped chefs, who should know better, into believing this. So unsuspecting home cooks now believe that Vidailia onions are a great cooking onion because the Food Network and other places have been telling hem this is so. They are not, sweet onions do not have the sugar content a good storage onion has, which is a big reason it will not store long term. They also do not have the chemical that makes you cry when you cut into one which is why they taste sweet and mild when eaten raw and do not give one heartburn. But when cooked sweet onions, because they do not have much sugar or the crying chemical, are insipid. They cannot caramelize due to lack of sugar (which is why most modern recipes call for the addition of up to a 1/4 cup of sugar in most modern onion recipes) and because they are lacking other chemicals found in abundance in a good yellow (hot) onion have insipid flavor. My favorite cooking onion is Copra, it has fabulous flavor. Unfortunately I will not be growing this onion after this season. Varsity, a new variety for us, also has great flavor when cooked and prince is almost as good. None of these varieties ever need the addition of sugar to caramelize and lend intense onion taste to any dish. Sweet onions should be used raw on sandwiches, burgers, hotdogs and in salads.