I think one of your issues is that the "loan amount" is not a fact that can aggregate over time using "Sum". You'll want to choose Last to get the "ending balance" of the loan. Payment amounts are additive over time so those facts should be ok.

Note - OBIEE doesn't do "last" the way I want it to. Instead of figuring out what the last value is based on the calendar, it pulls data down at (for instance) the day level...and then throws away all days data except the last. Thus to me it's a "value of the last day that had data" vs. "value of the last day". If you have users who like to bring down WAY too much data...then bringing it down at the day level, then throwing away all days except the last one, causes a LOT of data movement, and is very slow. The only way around this I've found is to define fact tables at each of the levels (day, month, quarter, year) and then using join tricks with the time dimension to "force" OBIEE to bring down the last value without doing a bunch of unnecessary work.

If you don't have users that bring down too much data, this may not apply....sadly I wouldn't know

Thx,

Scott