There are some companies that offer these that are unscrupulous. Talk to Realtors in your area and ask them if they have experience or knowledge in these type of transactions.
The homes I have seen sell through a lease option are often priced much higher than market value and are not contingent upon an appraisal. Lessees typically pay a higher rental amount, too, with a portion of that amount supposedly to be credited toward the down payment at a future date. If the company dissolves or files bankruptcy, that option money is gone and so is the extra principal paid toward equity.
I would strongly suggest that your friend hire a lawyer to review all documents in such a situation and never sign a single page without first obtaining legal advice.