Hi Dajana,
I have been browsing nongkhai map now for a long time, but have only just taken the plunge and signed up as you sound like you are in a similar situation to me a while back.
I am in my early 20's and like you, decided to throw a little adventure in my life and come to Thailand to teach, I really hoped to gain more life experience than anything else, but it really has turned out to become one of the best moves I ever made. I hope that I can make it last for many years to come.
I started my 1st teaching post about 18 months ago in Sangkhom at a small school on the banks of the Mekong. I made all the arrangements myself, I never knew about travel to teach or isara back then, but nonetheless I still managed to plan it all ok.
I have settled into the school now, and even get paid a small salary to keep me going, which I gratefully accept. They have been getting my visa fixed without any problems, so far

.
They have put me up in some local apartment where some other teachers stay, for free (it's basic, but good enough for me), and from what I can understand, they do rent for around 1300-1500 per month excluding water and electric that usually racks up to around 4-500p/m.
I eat and drink on the streets, so 100 or so baht per day looks after my food and drink requirements, and still allows me to save a few 000 baht per month to head into Nong Khai or Udon to let my hair down every now and again.
I have a motorcycle, Honda 110cc thing, cheap as chips to run, 50 baht per week for the gasoline.
An average month my outgoings total about 3,500 to 4,500 which also includes internet cafes and a few movies to watch here and there. I do live pretty simply though, but that way I look forward to my little weekends away to Nong Khai or Udon that much more.
Teaching here, is a nice deal, I was learning to teach back in the UK before coming here, so I am committed to the job, and I really enjoy it.
The ages of the kids I teach vary from 5 or 6 to around 12 when they leave for High School, and they seem to love me and my classes. It really gets tearful when some of the pupils leave to go elsewhere, there is such a strong 'family' feel to the area.
I think the only topic I didn't really touch base on was the travelling around thing, well buses go everywhere, and are very cheap and certainly work for me, as long as you're not too demanding, then you will have no problems getting around.
I have a local girlfriend up here as well now and she has a job in 7-11 that earns her some pocket money, so life is great for us in Sangkhom.
The only real things that I do miss are:
decent quality internet - it's really hit and miss up here, if it works at all that is
family - but they come to see me often enough
there are probably a few other things, but I cant think of them right now.
I think you will have a great time, so all I can suggest is DO IT!