If you are considering buying Boston real estate this fall, you will probably want to pay attention to the new Fannie Mae and Freddie Mac rules. Banker and Tradesman reported that "adverse market" fees will be doubled from one-quarter of a percentage point to one-half a percentage point starting Oct. 1 for new mortgages delivered to Fannie Mae, and Nov. 7 for loans delivered to Freddie Mac. That's $250 -$500 for every $100,000 borrowed. This will apply to all new purchasers and refinancers. However, if you have a FICO score of less than 720 and a down payment of less than 15 percent, you will be charged quarter-point higher fees upfront. So...if you are considering a purchase, keep these dates in mind.