People that expect someone like a bank or mortgage broker to figure out how much they can afford to pay monthly for a house are financially children and should never have had the opportunity to get into that much trouble. However, they are legally adults, and as such, need to take responsibility for their actions, as has been stated. We can't really have a test to see if people are smart enough to buy a house, gun, vote (most dangerous), have children, etc. Once you start requiring tests, etc., the shiny happy people in charge will game the system again and screw it up worse, consolidating their power even more.
Oh, and Bill, you have to understand the bean counting angle to know why banks do that. Having an undergraduate degree in Business, the bean counting courses were good for this. As my first bean counting instructor (Bean Counting from Hell 203) said, "You are not all going to be accountants [bean counters], but I can guarantee you that at some point you will be sitting across the table from an accountant and you need to know how he thinks." Thus, looking at this from the bean counter's point of view, this is what is going on: You pay your $100 principal and interest, broken down as $95 interest (profit) and $5 principal. You add an additional $50 to your payment. Instead of applying that to the principal, which would lower next months and all future months' interest (profit), that $50 is declared as going towards future payments. One of my student loans (THANKS, TEXAS) does this as a matter of fact and states it plainly on the statements. (STUPID TAX, even I was not immune to doing stoopid things like going to school and taking out loans to pay for it. I plan on winning by dieing before they're paid for - Woo-hoo, screw the man!) Anyway, lets say you add $50 every month. After 2 months, that's $100, a whole payment you are ahead. Instead of dropping the principal so your next $100 regular payment might be $90 interest and $10 principal, lowering the bank's profit on their statement, what they've done is declare that extra $100 as a future payment of $95 interest and $5 principal, taking that bill and declaring the future profit in this period/quarter/year. That's even better than not getting the extra money, from their financial statement point of view, as it's all about the short term profits and you just boosted their profit for this period. You, on the other hand are just screwed.
The lesson is: Yeah, you should make extra principal payments to game the system. BUT, you MUST pay super-close attention to the principal balance the bank is reporting. If you pay $50 extra, look at the principal balance and make sure next month that the prinicpal went down $50 (extra) plus $5 (regular payment to principal). Even if you write a separate check, noting in the memo field: "PRINCIPAL ONLY, YOU WORTHLESS, THIEVING MOTHERberkeleyERS," still check the principal balance every month. You never know when they might make a convienent "mistake" and just apply it to future payments. With the internet and online banking, it is a lot easier today to keep an eye on these things.