As for HIV, it's not a serious consideration in this situation, unless you (male) friend is bisexual, or if either he or your (female) friend use drugs by injection. If not, I really wouldn't worry about HIV
. But since you ask, here are two threads on the HIV
Prevention and Safe Sex forum that go into detail about timing for reliable test results. The bottom line is that for an antibody-only test, 6-8 weeks is enough time; for the antibody/p24 "combo" tests, it's 4 weeks.