If your company fails, you are not obliged to pay the money back, you can walk away. However, if you succeed to the point of getting your first round of funding

If your company fails, you are not obliged to pay the money back, you can walk away. However, if you succeed to the point of getting your first round of funding, then you have to pay back the money with interest. But I'm glossing over an important point. They really don't want their money back--they want equity in your company. So they will convert the loan to equity, however, they want up to a 25% discount on that equity. From an example on their web site, if they lend you $100,000 and you end up getting Series A funding, then they can convert that $100,000 loan into $137,333.33 of equity in your company. Your company's valuation will ultimately determine just how much of your company you are giving up for this money.