Assuming you have +100 you need to win 70.7% of the games to break even.
If I recall, in the NFL, ones that cross bothe 3 and 7 win something like 72 or 73% of the time..
This equivalates (Is that a word) to about 52.5% but against a +100 line... It is basically break even (I can't recall if it is like .1 up or down) on a -110 line.
I thought 7 pointers crossing both 3s would be profitable, but they are not.
In college, it is a horrible bet. I would estimate 47% at +100, but I have not run the numbers in a long time as I am certain there are no college teasers to play.
-Sean