Here’s how to deal with an annoying mooch who is otherwise a basically decent guy: Just say no. Don’t say why not; that invites negotiation. If asked why not, say no again, and ignore any uncomfortable silence. You do not want his request for a favor to turn into a dialogue. For example:
On a fine summer day Towne Mooch, who draws disability in spite of being able to work, for example as a greeter at Walmart like the guy in the wheelchair who’s greeting at Walmart… anyway, Towne Mooch approaches his latest mark: “Hi Mark, could you give me a ride home?”
Mark: “Sure, TM, hope in.”
TM: “Thanks! Can we stop at Walmart, and Burger King, and Jimbos for soda? Oh, and the post office.”
Mooch’s latest Mark: “No, not today.”
TM: “Why not?”
Mark: “Sorry, can’t do it.”
TM: “Oh… I don’t have any food in the house…”
Mark: ” ”
TM: “I wonder what I’ll do…”
Mark: ” ”
TM: “I guess I can walk two blocks down to the corner store and get something.”
Mark: ” ”
TM: “Thanks for the ride, Mark.”
Mark: “You’re welcome TM. Have a nice day.”
Monday Evening 
I once had an acquaintance at work ask me for a ten thousand dollar loan. The conversation went something like this:
him: “I need a 10,000 dollar loan.”
me: “Uh, I’m not going to cosign if that’s what you want.”
him: “No, no! I need the money.”
me: “oooh …. kaaaay….”
him: “So it’s OK?”
me: “If it’s OK with the bank it’s OK with me.”
him: “What does the bank have to do with it?”
me: “I mean the bank that is giving you the loan.”
him: “No, you are giving me the loan.”
me: “Me? You want me to loan you money? We don’t know each other that well.”
him: “But I’m ready to sign on a house and I need it for the down payment.”
me: “Maybe you should buy a house where you can afford the down payment.”
him: “I’ll pay you back.”
me: “Can’t say I have a lot of trust in someone who borrows money for a down payment. Sort of defeats the purpose of the down payment, you know?”
him: “I have to have the money by tomorrow or we will lose the house.”
me: “You know, it sounds like you can’t afford this house. You will probably be better off to let it go.”
him: “This house was a really good deal but we couldn’t get the loan terms we wanted”.
me: “I’m just not interested in sharing your financial woes. I’ve got my own.”
Looking back, I guess my strategy is to first play dumb, giving them a chance to get out gracefully, then to be brutally honest so they never try it again. Later found out that this guy mooched a total of forty or fifty thousand from various other people in the company that he barely knew. Don’t know if he ever payed them back.
Ten thousand dollars? I wouldn’t have been playing dumb; I’d have been struck dumb. That’s some amazing chutzpah.
… I wish I had your ability to say no. If I have an interaction point, I have a heck of a time saying no. Part of why Elf and I got together. (he defended me from street vendors at the ports)
Sometimes saying yes works out well:-)
Once, I accidentally made eye contact with one of those mall vendors in the middle of the aisle. I tried to look away, but it was too late. He said something and I said “No, thanks”. As I tried to walk away he got way closer than anybody should and stuck his hand out for me to shake, attempting to continue the conversation. I just stared at him, a little bewildered, and walked off saying “Sorry”. I probably could have been a bit more polite, but sometimes it seems like the only options are to be rude or to get wrapped up in it all and risk saying yes.
So they can maybe make a fast buck, these people abuse our impulse to be polite, degrading society in the process.
Just realize that this person has decided to victimize you in some way and intends to rely on your courtesy and sense of community in order to carry it off. Then realize that such a person doesn’t deserve a polite reply.
Easier said than done… I have a heck of a time managing it online, against those who make the most horrible accusations against me and mine. >.<