First, your guest are lucky they don't sleep down the street...it is very nice of you to put them up especially if you don't have the room.
I use a 2-hole punch and Prong Fasteners by ACCO (aluminum clips) to organize my papers. You can make the stacks as big as you would like. I will explain further in detail if you need me to.
I stopped using binders because the space they take. The fastener clips work fine.
If you are planning to sell and the house needs paint, then when you are ready to do so you can. It will definitely brighten the house. I find that my daughter does not fit in her clothes beyond the season, I usually just get rid of them when the season changes.
When I was younger and we lived in a small home, I was given a toy box and what I could fit was what I could have. Anything else, the first question was where will you put it.
If you want to paint the cabinets, double check with the hardware store. Explain what you have now or take a picture and see what can be done to change them.
How I feel about company anymore, is I can't be embarrassed for (in my case) a tidy home. It is clean in that restrooms & kitchen are clean, but maybe the laundry is not all done and perhaps not all put away. I used to really go out of my way to spend my entire day cleaning after working all day and keeping up a kid and a business and now I do what I can...if they don't like it, they can stay somewhere else. So if your kitchen is old and your company wants to eat someplace else, they can. If you have done all you can, then it is what it is.
When you are ready to sell this home you are in, you may need to get a small storage if you can't part with everything. Overcrowding makes a home look smaller than it is. The hangers inside the closets should have about an inch between them.
Best of luck.