Even though I own my own house, I find myself in this predicament. Besides my wife & I, my 2 adult children live here, along with my son from a previous marrage on weekends. Adults accumalate a lot more stuff than kids, if we ever had to move it would take 2 large trucks.
Think vertical, build your own racks for tanks, cages, or general storage. I have turned this into an art, having 4 full time & 1 part time adult living in a 3 bedroom house, with a 4th bedroom doubling as a fish room.
The 4th bedroom, which doubles as a fish room, or vice versa, has 12 tanks, a bed, set of shelfs, and computer desk. It's just shy of 8 foot by 16 foot, no betta size tanks. 3 10 gallons, 3 20 gallons, 4 29 gallons, and 2 55 gallons. You can still move around believe it or not.
I hate to see a youngster so interested in a hobby limited by space, measure out your room & furniture, draw the room to scale on a piece of paper, 1 inch=1foot usually works well. Do the same with the firniture, cut them out & rearrange the room on paper.
If you need a hand building racks or shelfs, pm me with what you're looking to do. I could scribble up something for you, no cad or anything like that, good old pencil & paper. You really can do more than you realize with a given space if you give it a little thought & planning.
Tolak