A home that has received a Notice Of Default is not yet for sale and the lender has no ownership of it until the property goes through foreclosure. I've chased dozens of homes that received an NOD, only to have the homeowner catch up with payments before I could snag it. I recommend you try this:
1. Find a local agent who can help you determine the market value of the property
2. Have the agent contact the homeowner to ask if they will look at unsolicited offers (many agents just send an offer to the owner, trying to be first in line, but I find the owner appreciates the soft sell and will cooperate more if you take it easy with them).
3.a. If the seller is in a short sale situation, work with the seller's agent to put the short sale package together for the lender and be patient
3.b. If the seller is willing to sell and is not in a short sale situation, have your agent begin negotiating and working towards opening escrow. You'll want to do a lot of inspections as soon as possible, since most homes that have mortgage lates also have lots of maintenance needed.
3.c. If the seller doesn't want to sell, make sure he has your contact information so he can call you if he needs help in the future.
4. Never, under any circumstances, get hood-winked into your agent representing you and the seller. If your agent suggests this to "make the transaction easier" or "to reduce costs" - I strongly, urgently recommend you consider another agent. The seller is in a distressed position and your potential liability increases greatly because of it. Bringing dual agency into the deal just adds to the possibility of you ending up in court and/or losing the property. In the end it will not make things easier and it probably won't save you very much money.
Lastly, listen to your local agent to find out if there are any better ways about going after NOD's in your area. I'm a northern California agent, I can't help you with your deal, but the advice I provided applies in any market. Just add to it any localisms your good agent suggests.
Best of luck!