First off, are you a SEARCH or ISS candidate? This is critical information because if you are registered with either of these organizations, refusing a contract after agreeing by email to accept it could have very serious repercussions as both of these organizations will blackball teachers who renege on their contracts. They do so within their own organizations and they also have done so by notifying other organizations recruiting international teachers. This makes the situation for teachers who do not follow through on written/verbal contracts very difficult indeed!
Acceptance by email is legally binding. What you could do is to contact the Principal of the school, explain the situation to him/her and see if the school can prepay your airlines ticket and VISA. I can understand that the school may not want to cut you a check in advance because if you choose to not follow through on your commitment the school is then out money with no way to recoup. On the other hand they are not showing much confidence in you and this would make me question the quality of the school.
In my experience, most all schools supply you with visa money and airline tickets in advance of your departure. Most schools work with a travel agent that will make all the necessary arrangements, book your flight and forward your tickets to you. My hunch is that the school you are talking with has had bad experiences in the past with teachers not following through and this would make me a little suspicious concerning the nature and quality of the school. In consulting with members of the International Schools Review staff I discovered that none of them had ever had to purchase their air tickets out of their own money and then wait for reimbursement. One member reported that he actually received a check for six thousand dollars at the fair and was instructed to purchase tickets and visas for himself and family and keep whatever money was not spent.
I recommend you email the director and explain the situation. Ask him/her to have their travel agent make a reservation for you and forward by Internet the e-ticket. You can then also demonstrate good faith and handle the visa expenses on your end and be reimbursed upon arrival. I’m certain the director will realize your sincerity and efforts, understand your financial situation and thus be willing to help you.
Does this answer all of your questions? If not, come back to me for clarification.