re: Dividing up rent in an apartment

Bill is going to be looking for someone to split his room with. Two couples would be great. I'm sure John/Jane would love Bill's chick moving in.

The fairest way (but certainly not the easiest) would be as follows: Measure the sf of the "private" areas and the "common" areas. Jane and John should pay their private sf/total private sf, plus (2/3rds of common sf/total common sf) x rent. "Private" sf would be the total sf of bedrooms and baths used exclusively by one party or the other. "Common" sf would be living room, kitchen, dining area, i.e., those rooms used (or available to be used) by everyone in the apartment. Since it's Jane and John's apt, they should very easily be able to take all of the measurements themselves, do the arithmetic, and say "Bill, this is what you pay if you want in". If Bill is curious about the split, show him the math. I assure you, there is no fairer method than this.