Your APR will not say how long your rate is locked in, so check this. A short-term lock of ten days should be offered at a lower APR than a longer-term lock of a month or more. Adjustable and balloon loans make it hard to calculate real APR because future rates are unknown. In general, though, a lower APR is going to be a better lender.

Fifteen and thirty year loans are not comparable through APRs. And not all lenders know what is included in the APR because it's all done through company software. The same lender may use two software programs to calculate APR – and come up with two different numbers.

An APR is not the price on the shelf for a loan. It's only a starting point for loan comparison, and should be viewed as the result of a complex, obscure calculation. A good-faith estimate from your lenders is the best way to compare costs.