I'll have to upload some pics of the storage unit next time I get out there...but here's some of the storage history...
When I first started out, I was just stacking sets in a closet, on the floor, next to the bed, etc. That got old pretty quick, so I got a set of shelving from Home Depot...at this point my friends said I was crazy and had "taken it too far". They are a little under $40 or so per set. They are 36" wide x 18" deep.
I like these because the normal "large' sets like HP Hogwarts, Helm's Deep, etc. will fit almost perfectly without the top shelf touching. I ultimately ended up with 7 sets of shelving in the house before I had to get a storage unit...now I have 5 sets of the shelving at home:
Pardon the mess! I just moved a couple of months ago and am still getting my workspace setup, and some of the orderliness has gone out the window this month. Essentially I use the shelves at home to hold things that I'm going to list on eBay relatively soon...everything else goes to the storage unit. Eventually I'll have a work table setup in this room for packing, etc. I buy boxes from Uline in bulk in a range of sizes that match up well with the different set boxes that Lego puts out...for the big ones like Helm's Deep I do 24x16x4, for Winter Toy Shop 20x16x4 and so on. Bubblewrap comes from Amazon or eBay depending on who is cheaper, plus packing tape. I've got a cheap postal scale and use an old Zebra thermal label printer to print my Fedex/USPS labels on...I have a ton of free label rolls that UPS gave me a few years ago, so I still use those.
Once you get to any kind of regular volume, standardizing packing materials saves a bunch of time. I used to stomp through the house trying to find a box to pack a set in, or cut a box down, etc. etc. With the standardized boxes, the packing becomes a no-brainer. It does require a little investment (Uline will ship free for orders over $250 or $300...they have a warehouse in my area tho so I can pick up for no charge), but the time savings is immense. I recycle packing materials when I can, but the purchased bubblewrap makes it a lot easier...I need to find a cheaper source since I use alot.
The storage unit is a 10x10 in a climate controlled facility (basically just a big heated/cooled warehouse that they subdivided into individual spaces). I've got 10 shelving units lining the side and back walls, with a folding table set up for staging. I may need to put in a couple more shelving units as space got real tight after last year's Christmas clearances.
I always unpack sets and don't store them in Amazon/TRU shipping boxes...too much air (makes for inefficient storage) and i like visually seeing the sets so that I can quickly pull some if my stock is running low at the house. I will usually make a trip at the start of the week out to the warehouse to unload/unpack new purchases and to bring home anything i intend to sell.