This is generally a common concern for someone looking to work from home, so here it is.
When you say, work at home, it could translate to a number of different things. For the sake of this example, I will use the most common. There are wah JOBS & wah BUSINESS OPPS.
WAH Jobs...this would consist of you being hired as an employee to do your work from home. With this, you are paid either an hourly wage, or salary. You get paid for the work you do and the hours you put into it. You should NEVER have to PAY someone to work for them, or in other words to get the "job."
WAH Business...this is exactly what it says, a business you own that is done from home. There are a number of different businesses that you can do, typically it's any company whether it be mlm or network marketing, that offers a product or service that you in turn market. This is how they differ, with a business, you are not paid for the time you put into it, you are paid for results. It doesn't matter if you put in 100 hours or more, if you do not get anything in regards to "sales" you are not paid. On the flip side of that, all of the work that you do put in, is yours and you continue to get paid without ever having to do the work again. This IS something that you would PAY to do, because you are getting things in return.
What about Pyramid schemes? First of all they are illegal and are based on taking advantage of people. For a person to make money in a pyramid scheme, someone else has to lose money. Typically with a pyramid scheme, there is no product involved at all.
There are many different types of wah jobs and businesses to choose from. My suggestion would be to do your research, find a company that you can actually see yourself getting excited about what they offer, ask questions, and in the end it will most likely take a bit of trust in yourself and faith that you can be successful. With the right tools and training, anything is possible.