I don't remember how Milos works. Is he the biker guy?
To meet Last Man, you have to find the Last Man graffiti around town. First it appears by the dock. Touch it and you'll see a message. A few days later (it's random, maybe 5?) It will appear somewhere else. Touch it again. This happens 3 times. One of the locations is near the curry shop if I recall correctly.
After finding 3 graffiti, Last Man will appear near the the Northside of the city. Then you have to give him money to start raising his friendship.