All 3 would be of help! Start networking and keep a notebook or such of contacts in all fields!
Driving around neighborhoods for vacant/rundown properties..get the street name and address..look it up at your court house (online maybe too) and see what they paid and when...if it makes sense, write the owner and put and not on door too!
Also, at your local court house...check out the foreclosure listings..usually new ones added every Wednesday!
Check out the ones that makes sense in what form of RE investing you are doing! Most times, it's best to go to the home owners house (with a buddy) and meet face to face and show them your solution(s)!
Gotta run..hope this helps!