You have to ask yourself, in what kind of circumstances would you be able to buy at a discount sharp enough to provide yourself with a profit, the angel investor with a return on his/her investment, and still have a price that is attractive enough to the eventual Buyer to think this is worth his investment, as well? Peter Ireland (writer below) is correct, in that the amount of time and what you could do to add to the value are key.
Carl Icahn does this with some frequency. However, he does this with mammoth corporate conglomerations, where he tears the assets apart and sells them individually. The parts, in these cases, are worth more individually than they are in a singular entity. With small business, this is impossible. And since you are asking this question, in a public setting like this, voicing the need for an angel investor to accomplish your goal, it is assumed you are not in that league.
And by the way, Carl Icahn - who is a bit of a personal hero - is probably one of the most sued people in the Country. At his level, being sued is simply a cost of doing business. In small business, that would not be the case. Being sued is like playing horseshoes, in that "close enough" still costs you a bundle; even if you win your case, the cost of defending yourself can cost far, far more than the profits of this kind of high risk scenario.
There was one example that comes to mind. A Buyer found out the Seller had a terminal disease, and took advantage of the situation by telling him that the Buyer could settle in thirty days, but to do so, he wanted a very deep discount on the price. About a week before the proposed settlement, the family of the Seller found out what was going on and threatened to sue. Imagine going into a court and trying to defend yourself against charges that you were dealing with a desperate, terminally ill man, possibly under the influence of drugs that might impare judgement, all in the interest of your own, personal gain, to the extreme disadvantage of a man on his deathbed and his berieved family...
Who is going to win?
Are there other circumstances where there is less risk? I can't think of any, off the top of my head. I would go very carefully into a deal with this kind of philosophy.