All great responses!
I can tell you most of the big boys are looking for equity, and if a property isn't a "clean" deal with 30%+ equity they'll tend to pass it over.
We've been very successful with marketing to sellers that have little to no equity. They can't be upside down but ideally they'd have $5K to $20K in equity.
You find these sellers by targeting the expired listing in the MLS. The seller is motivated and is open to creative solutions.
Here's the strategy which is nothing new: Send the seller a Yellow Letter telling them you want to buy the house. When you meet with them negotiate to keep the existing loan in place for up to 3 years and give them $1,000 to $2,500 cash.
Your essentially buying the property "subject to" the existing loan.
Once you have the deal tied up you can then market the property on Craig's Lists offering 'No Qual Seller Financing" your looking for a retail buyer that has $10K to $15K as a down payment.
You then assign the contract to the new buyer for the difference between what you agreed to pay the seller and the down payment. ($15,000 down payment - $2,500 cash to seller = $12,500 profit)
This in any market is a HUGE opportunity. Just be sure you have the title company service the loan by collecting the payments from the buyer and pay the sellers mortgage company. This way everything is audited.
Do be aware that most bank have the right to call the note "due on sale" although I've never heard it happen.
Hope this helps,
Cheers :)
Sean