Fair enough on all the above about direct debit, but just keep in mind that b/c you wont do something doesnt mean others wont. Plenty of people love using direct debit. I dont own a TV. I hate watching TV. Plenty of people love it.
I think a model that might work for lower income people would be a private label credit card if such a thing still exists. This kind of card was used for luxury purchases by people who couldn't get a visa or mastercard and were lured in by in-store financing for appliances, furniture, jewelry, etc. The salespeople in such establishments were often able to see how much credit the customer had available and up-sell them accordingly.
You did say this:
"No customer in their right mind would let a small business do direct debit or automatic withdrawal or whatever you want to call it."
When someone isnt in their right mind to do something it implied to me it was "stupid to do"...I guess that's what I call someone who is "not in their right mind". and I simply replied to say plenty of people do direct debit for things to gym membership, to magazines to skin care.
I dont think b/c someone does a pmt plan they are always a low end client. Life isnt a one size fits all. I like to think that the guy who can afford a BMW But doesnt PIF isnt a cheapo, the pmts just work better. Sure he doesnt have $30,000 or whatever, but he's not a low end client either. He's still buying a BMW. But in some cases you could cater to a low end market with payments and that is NOT what I am talking about doing.
possibly so, but it never hurts to think outside the box.

