Well Jed Smith, composer of the Angelas World 2 Soundtrack, did it like this:

15 second intro of a song, and then one minute looping. So i can fade in the intro and let the other part run in a loop.

I don't think endings are good for INGAME music, except they are for action scenes with an end. It's always depending on the customer. You could also offer more version. One with intro and loop, one with start and ending, one long version with start and ending, etc.

EDIT:
BTW, just to compare, Jed Smith sold the songs for 50 dolla each song, with exclusive rights. So this is actually cheap, you can even get 100 euro if it's for one game exclusive.

I bought another soundtrack from a public website and i paid 40 dolla for 7 songs. Everyone else can buy these songs too and use them in commercial projects (but when you sell too many copies of it, you have to get another license which is more expensive).

So i would pay maybe up to 60 euro for a cd with 10 songs if it's not exclusive for my game.