In my experience, this is rarely worthwhile as 99% of startups don't even get funded, and without an anti-dilution guarantee (which requires an irrevocable modification to the by-laws of the company, and is STILL not a guarantee), you're unlikely to see anything from the venture.
What I would suggest is convertible equity. Take the stock, but get in writing that if the stock isn't worth X by date Y, you have the right (but not the duty) to convert it to debt, payable upon presentation, with a 1.5% per month interest rate if not paid immediately.
You're still unlikely to see a dime, but at least you can sell the debt to a collection company if things get bad.
