You might want to start with a website that is more oriented to your particular question. (see e.g., association of shareware professionals

You said ...

I have this idea of a program that may become very popular.

I never actually programmed anything that was for sale or even as freeware.

I am planning to make this script purchasable for under 40$.

• a great idea does not automatically translate into great software
• great software does not automatically translate into recognition
• recognition does not automatically translate into sales
• sales do not automatically translate into profits
• profits do not automatically justify the specific effort required to make them

If you do not have any experience with commercial software, you have some homework to do before a lawyer will take you seriously enough to even take your money from you. try reading some Joel for example. You might do well to see a lawyer, as they will have the professional duty not to disclose confidential info, but even then you have to do your homework first.

If your *best* projections for this project of yours is $400,000 tops, you may be better off selling this great idea of yours to an existing company and let them develop, market and deploy your solution. No matter what path you take, you are going to have to reveal the secret to someone with more experience than you sooner or later ... which means working your butt off no matter how you look at it.