@josh0335,
i think exploitation is the unethical part. you can loan money for a fair sum as in rent, but to loan money to people you know will never have the money to pay you back and then take their property is unethical. that is the oversimplified explanation.
i wouldnt ask money as interest from my family, but they have asked me and i have paid it without flinching because if they took it out of where it was being kept so i could use it, they would be losing interest or other form of income that it provided them. too often people become greedy and instead of using their own money for projects they let it work for them and bring income while borrowing money at a rate of interest that is less than what is being generated by the money they have in order to accomplish their plans. this may seem particularly smart, but it can also become a way of exploiting the lender.
both the lender and the borrower can be exploited when interest is involved. it is easy to say let them beware and be educated, but laws have grown up to protect those who are not able to make informed decisions and sometimes penalize the innocent in the process.
in a perfect world, no one would have to lend or borrow. those with an overage would freely and gladly give to those who had less. but i dont think that world will happen on this earth-
and as aedes brought up, i would never have been able to buy a house had it not been for the bank giving me the wonderful opportunity of paying three times as much as it cost by charging interest so they could give me no interest at all in my bank accounts. it sounds like a person would be crazy to do something like that, but it was cheaper than paying rent on an apartment. life really isnt fair, is it!
there are a lot of other business that i think are unethical which people dont even mention, for instance insurance. they seem pretty much unethical all the way around, their principles for making money are unethical. come to think of it, i think all ideas for making money are unethical. money itself is unethical. what about all the businesses that manufacture things that dont even work, like miracle cures for this and that, a la late night television ad programs?