I'm staying alone at home. Can I learn martial arts on my own? It's dangerous in the place where I'm staying. There are many thefts. I want to learn Martial Arts on my own because I'm poor. I can't pay a fee. Also there are fewer teachers in my area. Any suggestions?
Can I learn martial arts by own?
Yes you can - but all you will have is an academic knowledge of the art, you won't be able to rely on it to defend yourself. To be honest you will probably hurt yourself more than your opponent if you relied upon it without some expert instruction.
You can read all the books and watch all the youtube clips you want, but it's going to take time to get good enough to be able to actually use the martial art you learn. Learning a martial art in this way could be outright dangerous - it may give you a false sense of security and get you into a situation you would normally have avoided.
If moving to a different area as Keith suggested is not an option, then you should look to the community - there will be someone who will have some knowledge. Look to high schools/colleges/universities, they may have clubs. Somewhere there will be at least a boxing club. Even a weightlifting club would be an option if there were no fighting oriented clubs.
I'm financially ill, I can't pay fee
Instructors need to eat and possibly feed their family. But even so there will be something you can work out with the instructor if you needed to; for example you could barter some work for lessons. If you are genuine with your need and intentions I think most instructors would find a way to fit you in.
You can learn some things alone. But there's a lot of caveats worth noting.
Self defense is risk reduction
Martial arts can give you some tools, but it's worth noting that the best safety is avoiding danger where you can.
So - the best training you can do alone right now is finding away to get yourself up on some short distance sprint training. Obviously, if your neighborhood isn't safe, it may make that difficult - but running IS a great skill to have trained.
Also realize that getting robbed is unpleasant, but not the real problem - it's people trying to hurt you that you really have to worry about. It's not worth getting into fights if someone is going to take your money.
Things you can learn without a teacher
Do you have a friend or a family member who would be willing to practice with you? That helps.
The thing you can generally train is how to push people. Push them with your hands, push them with your forearms, push with a shoulder check, push with your hips. If you can shove someone and run, you have a simple skill you can use.
You can look up stuff online like Tony Blauer's S.P.E.A.R. defense videos - he uses a simple move that works well for that kind of thing.
If you don't have a friend to work with... well, you can try practicing your shoves against things like poles or indoor building supports or the frame of a doorway. That said, all of this basically boils down to shove and run.
A simple tool
The last thing, is you can get yourself a small, heavy flashlight. A 5-7 inch Maglite usually is small enough to go in a pocket, heavy enough you can get an effect from it using a hammer fist (grip the flashlight, hammer it down on someone) and they're usually not more than $20 tops, making it more affordable.
Again, the goal of using this would be a stun and run - hit them, push them, run.
There might be more people in your area who want to train
What a lot of folks don't realize is that there usually is a fair number of folks who want to learn self defense, especially if the area is not great. I would definitely do some searching online - craigslist, meetup.com, etc. (or the equivalents if you're not in the US) to see if you can find a study group in your area. You might want to ask around at places like a YMCA, any churches/temples/mosques and if there's any local community colleges to see if anyone has leads as well.
Many of these groups charge nothing, or a very minimal fee compared to martial arts instructors or schools. I know my first serious teacher would teach women and youth for free and we trained in a church basement for many years.