I suggest thinking of it as a balcony or patio tree. I am assuming that where you took the photo is on your balcony?
How large a bonsai do you want to end up with? Acer rubrum is probably best in larger sizes, shoot for at least 24 to 40 inches tall. At larger sizes the proportion problems red maple has with overly long leaf petioles will be less obvious. It will be more than hardy enough to leave outside through winter. Do not protect it from cold, it needs every minute of near freezing and below freezing it can get to help meet dormancy requirements. Protect it from cold and it will slowly weaken and die.
For a tree that is 24 to 40 inches in diameter, you will want a trunk that is at least 4 inches in diameter, preferably 6 or more inches in diameter. When you set a beer can or soda can next to the trunk, it should be larger in diameter than the can. So for the time being you should be just letting it grow. You can let it grow tall, which might get unwanted attention from the land-lord or the homeowners association. Or you can force it to get bushy. Search this site, and read Walter Pall's blog about Hedge Pruning maples. What increases the diameter of the trunk is the total leaf surface area. The more leaves, the more surface area, the quicker the trunk will increase in diameter. So the more branches, the more leaves, the quicker the trunk will increase in diameter.
Also, this trunk is very straight, without movement or any interest. Here is what I'd do.
year one - Prune trunk off at roughly 4 to 6 inches tall. Seal the wound. It is okay to do this now. Use cut paste, or Elmer's wood glue, or Duct Seal, or any of the many sealants suggested. The tree should take 4 to 6 weeks, and will send out many back buds. You want to keep any back bud more than an inch above the roots. Remove any root suckers, or shoots growing from the point where the roots join the trunk.
Let these shoots grow wild all year. in the mean time, you can think about style you might want to shoot for. Informal upright? Broom?, Informal Broom? What ever style you like. I would avoid styles like literati, windswept, and slanting, as these have quirks that make them hard for a novice to pull off. Also the tree will resist being made into a cascade. I would forget that one too, though it could be done.
2020
Late winter, while leafless, look at the branches that grew the year previous. Prune off any obvious problems. Multiple branches from the same point should be reduced to a single branch. You are not styling the tree yet, so don't pick a front or back, don't worry about that. You need lots of growth and you probably will not keep any of the first sets of branches in the final design 10 years down the road. It can be styled the first time by about 5 years, but the second styling at about 10 to 15 years will be the one that makes it an exhibition tree. SO don't worry about front, back or style, not right away.
Late winter 2020 hedge prune - Remember how short you pruned the trunk? If you cut it to 4 inches, no branch should have a straight section longer than two thirds this 4 inch distance. Hence, 3 inches would be maximum visually acceptable straight segment of branch. Now cut every 2019 branch to roughly 3 inches in length. This will force branching, and it will force more back budding from the trunk.
2020 - repot to larger pot - work out the roots, arrange a radial root distribution, like spokes of a wheel. Do not expose the roots, nebari,, Instead bury the roots. You need to keep the nebari buried by at least half inch for the first 5 years or so.
Let it grow for 2020
late winter 2021 - repeat the branch selection as outlined above. Where branches branch, if there are 3, reduce it to 2. Awkward branches must go. Then prune to less than 3 inches. Actually, the 2020 segments of a branch should be pruned to be about two thirds the length of the 2019 segments, so if they were 3 inches, the next segment should be 2 inches. This pattern of shorter and shorter segments should repeat ''ad finitum'', but of course, we are really only doing this the first 5 to 10 years, it will work out.
Repot to larger pot if needed.
This cycle of grow out, prune back needs to be repeated for about 5 years. You should have a dense ball of branches and foliage, maybe 36 inches in diameter. When you to your first styling somewhere around year 5 to year 7 you should have dozens, maybe as many as 30 to 50 branches to choose from to create your lines. You will remove 90% of the tree at that point. But you should have lots of good choices. wiggly branches because they were repeatedly pruned to prevent long straight runs. It will work out nice.