If you had access to $500m then I could make a pretty guaranteed greater than 8% return but it won't work with less. A mining company where I have purchased some junk bonds (12.5% coupon) has the bonds trading at 44% of par (so essentially they are paying 28% or so).
The company is struggling, like all mining companies are (they mine copper and gold) however they do make just enough to cover the interest payment, taxes, and other expenses. They have about $200m cash on hand, and $900m in bonds, with the common stock worth $100m. They have revenue from the copper and gold of around $380m a year with a operations cost of $270m a year.
Ok, so the plan is to slowly buy up the bonds at 40% to 50% of par with a good portion of the $500m while setting up a few entities to also buy up the common stock. When you own 25% or so of the common stock and 80% of the bonds, announce a plan to refinance the bonds at 8%. You will have turned the $500m into about a billion.