@Gojja81

Its good that money is less important for you because the bases you will use for an exposed hairline are by nature more fragile. Working out doesn't wear them down by the detachment / reattachment routine you will need to follow is what will wear the base down.

Also take into serious consideration everything rashton83 is saying: if you aim for 100% undetectability you will never be satisfied - you can come very close to 100% though and keep in mind that average people don't study things very closely unless their attention is drawn to it. Intense light like the sun and prolonged periods around people are some of your biggest enemies with an exposed hairline, with the de/reattachment routine being your biggest concern.